Electrostatics Online Test 12th Science
Electrostatics Online Test 12th Science
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Question 1 of 90
1. Question
The forces we experience in everyday life are electromagnetic in nature except ____
Correct
The technological developments of the modern 21st century are primarily due to our understanding of electromagnetism. The forces we experience in everyday life are electromagnetic in nature except gravity. It is now understood that except gravity, all forces which we experience in every day life (tension in the string, normal force from the surface, friction etc.) arise from electromagnetic forces within the atoms.
Incorrect
The technological developments of the modern 21st century are primarily due to our understanding of electromagnetism. The forces we experience in everyday life are electromagnetic in nature except gravity. It is now understood that except gravity, all forces which we experience in every day life (tension in the string, normal force from the surface, friction etc.) arise from electromagnetic forces within the atoms.
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Question 2 of 90
2. Question
Which among the following statement is correct
1) When an object is pushed, the atoms in our hand interact with the atoms in the object and this interaction is basically electromagnetic in nature. When we stand on Earth’s surface, the gravitational force on us acts downwards and the normal force acts upward to counter balance the gravitational force.
2) It arises due to the electromagnetic interaction of atoms on the surface of the Earth with the atoms present in the feet of the person. Though, we are attracted by the gravitational force of the Earth, we stand on Earth only because of electromagnetic force of atoms.
3) When an object is moved on a surface, static friction resists the motion of the object. This static friction arises due to electromagnetic interaction between the atoms present in the object and atoms on the surface. Kinetic friction also has similar origin. This branch of electricity which deals with stationary charges is called Electrostatics.Correct
Incorrect
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Question 3 of 90
3. Question
Two millenniums ago, Who, noticed that amber after rubbing with animal fur attracted small pieces of leaves and dust?
Correct
Two millenniums ago, Greeks noticed that amber (a solid, translucent material formed from the resin of a fossilized tree) after rubbing with animal fur attracted small pieces of leaves and dust. The amber possessing this property is said to be ‘charged’.
Incorrect
Two millenniums ago, Greeks noticed that amber (a solid, translucent material formed from the resin of a fossilized tree) after rubbing with animal fur attracted small pieces of leaves and dust. The amber possessing this property is said to be ‘charged’.
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Question 4 of 90
4. Question
Which among the following statement is correct
1) Consider a charged rubber rod hanging from a thread. Suppose another charged rubber rod is brought near the first rubber rod; the rods repel each other. Now if we bring a charged glass rod close to the charged rubber rod, they attract each other.
2) At the same time, if a charged glass rod is brought near another charged glass rod, both the rods repel each other. From these observations, the following inferences are made (i) The charging of rubber rod and that of glass rod are different from one another. (ii) The charged rubber rod repels another charged rubber rod, which implies that ‘like charges repel each other’.
3) We can also arrive at the same inference by observing that a charged glass rod repels another charged glass rod. (iii) The charged rubber rod attracts the charged glass rod, implying that the charge in the glass rod is same kind of charge present in the rubber. Thus, like charges attract each otherCorrect
We can also arrive at the same inference by observing that a charged glass rod repels another charged glass rod. (iii) The charged rubber rod attracts the charged glass rod, implying that the charge in the glass rod is not the same kind of charge present in the rubber. Thus unlike charges attract each other.
Incorrect
We can also arrive at the same inference by observing that a charged glass rod repels another charged glass rod. (iii) The charged rubber rod attracts the charged glass rod, implying that the charge in the glass rod is not the same kind of charge present in the rubber. Thus unlike charges attract each other.
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Question 5 of 90
5. Question
In the 18th century, who called one type of charge as positive (+) and another type of charge as negative (–)?
Correct
In the 18th century, Benjamin Franklin called one type of charge as positive (+) and another type of charge as negative (–). Based on Franklin’s convention, rubber and amber rods are negatively charged while the glass rod is positively charged. If the net charge is zero in the object, it is said to be electrically neutral.
Incorrect
In the 18th century, Benjamin Franklin called one type of charge as positive (+) and another type of charge as negative (–). Based on Franklin’s convention, rubber and amber rods are negatively charged while the glass rod is positively charged. If the net charge is zero in the object, it is said to be electrically neutral.
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Question 6 of 90
6. Question
Charging the objects through rubbing is called _____
Correct
When an object is rubbed with another object (for example rubber with silk cloth), some amount of charge is transferred from one object to another due to the friction between them and the object is then said to be electrically charged. Charging the objects through rubbing is called triboelectric charging.
Incorrect
When an object is rubbed with another object (for example rubber with silk cloth), some amount of charge is transferred from one object to another due to the friction between them and the object is then said to be electrically charged. Charging the objects through rubbing is called triboelectric charging.
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Question 7 of 90
7. Question
The SI unit of charge is ____
Correct
Most objects in the universe are made up of atoms, which in turn are made up of protons, neutrons and electrons. These particles have mass, an inherent property of particles. Similarly, the electric charge is another intrinsic and fundamental property of particles. The SI unit of charge is coulomb.
Incorrect
Most objects in the universe are made up of atoms, which in turn are made up of protons, neutrons and electrons. These particles have mass, an inherent property of particles. Similarly, the electric charge is another intrinsic and fundamental property of particles. The SI unit of charge is coulomb.
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Question 8 of 90
8. Question
Which among the following statement is correct
1) Benjamin Franklin argued that when one object is rubbed with another object, charges get transferred from one to the other. Before rubbing, both objects are electrically neutral and rubbing simply transfers the charges from one object to the other.
2) He concluded that charges are neither created or nor destroyed but can only be transferred from one object to other. This is called conservation of total charges and is one of the fundamental conservation laws in physics.
3) It is stated more generally in the following way. The total electric charge in the universe is constant and charge can neither be created nor be destroyed. In any physical process, the net change in charge will always be zero.Correct
Incorrect
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Question 9 of 90
9. Question
Who in n his famous experiment found that the value of e = 1.6 × 10–19 C?
Correct
Robert Millikan in his famous experiment found that the value of e = 1.6 × 10–19 C. The charge of an electron is −1.6 × 10–19 C and the charge of the proton is +1.6 × 10–19 C.
Incorrect
Robert Millikan in his famous experiment found that the value of e = 1.6 × 10–19 C. The charge of an electron is −1.6 × 10–19 C and the charge of the proton is +1.6 × 10–19 C.
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Question 10 of 90
10. Question
Calculate the number of electrons in one coulomb of negative charge?
- n = 1.38 × 1018 electrons
- n = 3.18 × 1018 electrons
- n = 6.25 × 1018 electrons
- n = 9.18 × 1018 electrons
Correct
According to the quantisation of charge, q = ne
Here q = 1C. So, the number of electrons in 1 coulomb of charge is n = q / e.
n = 1C / 1.6 ×10-19
n = 6.25 × 1018 electrons.
Incorrect
According to the quantisation of charge, q = ne
Here q = 1C. So, the number of electrons in 1 coulomb of charge is n = q / e.
n = 1C / 1.6 ×10-19
n = 6.25 × 1018 electrons.
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Question 11 of 90
11. Question
Which among the following statement is correct regarding coulomb’s law?
- In the year 1786, Coulomb deduced the expression for the force between two stationary point charges in vacuum or free space. Consider two-point charges q1 and q2 at rest in vacuum, and separated by a distance of r. According to Coulomb, the force on the point charge q1 exerted by another point charge q2 is F21 = K r12.
- Coulomb’s law states that the electrostatic force is directly proportional to the product of the magnitude of the two-point charges and is inversely proportional to the square of the distance between the two-point charges.
- The force on the charge q2 exerted by the charge q1 always lies along the line joining the two charges. r12 is the unit vector pointing from charge q1 to q2. Likewise, the force on the charge q1 exerted by q2 is along r12 (i.e., in the direction opposite to r12). The magnitude of the electrostatic force between two charges each of one coulomb and separated by a distance of 1 m is calculated as follows: |F| = 9 × 109
Correct
In the year 1786, Coulomb deduced the expression for the force between two stationary point charges in vacuum or free space. Consider two-point charges q1 and q2 at rest in vacuum, and separated by a distance of r. According to Coulomb, the force on the point charge q2 exerted by another point charge q1 is F21 = K r12.
Incorrect
In the year 1786, Coulomb deduced the expression for the force between two stationary point charges in vacuum or free space. Consider two-point charges q1 and q2 at rest in vacuum, and separated by a distance of r. According to Coulomb, the force on the point charge q2 exerted by another point charge q1 is F21 = K r12.
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Question 12 of 90
12. Question
By Coulomb’s law, in S.I units, k = and its value is _____
- 9×109 N m C
- 9×109 N m2 C
- 9×109 N m C2
- 9×109 N m2 C–2
Correct
By Coulomb’s law, in S.I units, k = and its value is 9 ×109 N m2 C–2.
Incorrect
By Coulomb’s law, in S.I units, k = and its value is 9 ×109 N m2 C–2.
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Question 13 of 90
13. Question
Which among the following statement is correct regarding coulombs law?
- Coulomb’s law has same structure as Newton’s law of gravitation. Both are inversely proportional to the square of the distance between the particles. The electrostatic force is directly proportional to the product of the magnitude of two-point charges and gravitational force is directly proportional to the product of two masses.
- But there are some important differences between these two laws. The gravitational force between two masses is always attractive but Coulomb force between two charges can be attractive or repulsive, depending on the nature of charges.
- The gravitational force between two masses is dependent of the medium. For example, if 1 kg of two masses are kept in air or inside water, the gravitational force between two masses remains different. Thus, electrostatic force between the two charges depends on nature of the medium in which the two charges are kept at rest.
Correct
The gravitational force between two masses is independent of the medium. For example, if 1 kg of two masses are kept in air or inside water, the gravitational force between two masses remains the same. But the electrostatic force between the two charges depends on nature of the medium in which the two charges are kept at rest.
Incorrect
The gravitational force between two masses is independent of the medium. For example, if 1 kg of two masses are kept in air or inside water, the gravitational force between two masses remains the same. But the electrostatic force between the two charges depends on nature of the medium in which the two charges are kept at rest.
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Question 14 of 90
14. Question
What is the value of Gravitational constant?
- G = 4.91 × 10–8 N m2 kg –2
- G = 5.82 × 10–11 N m2 kg –2
- G = 6.67 × 10–11 N m2 kg –2
- G = 7.83 × 10–11 N m2 kg –2
Correct
The value of the gravitational constant G = 6.67 × 10–11 N m2 kg–2. The value of the constant k in Coulomb law is k = 9 × 109 N m2 C–2. Since k is much greater than G, the electrostatic force is always greater in magnitude than gravitational force for smaller size objects.
Incorrect
The value of the gravitational constant G = 6.67 × 10–11 N m2 kg–2. The value of the constant k in Coulomb law is k = 9 × 109 N m2 C–2. Since k is much greater than G, the electrostatic force is always greater in magnitude than gravitational force for smaller size objects.
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Question 15 of 90
15. Question
Which principle explains the interaction between multiple charges?
Correct
Coulomb’s law explains the interaction between two-point charges. If there are more than two charges, the force on one charge due to all the other charges needs to be calculated. Coulomb’s law alone does not give the answer. The superposition principle explains the interaction between multiple charges.
Incorrect
Coulomb’s law explains the interaction between two-point charges. If there are more than two charges, the force on one charge due to all the other charges needs to be calculated. Coulomb’s law alone does not give the answer. The superposition principle explains the interaction between multiple charges.
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Question 16 of 90
16. Question
Which among the following statement is correct regarding superposition principle?
- According to this superposition principle, the total force acting on a given charge is equal to the vector sum of forces exerted on it by all the other charges. Consider a system of n charges, namely q1 , q2 , q3 ….qn. The force on q1 exerted by the charge q2,
- F12 = K r21. where r21 is the unit vector from q2 to q1 along the line joining the two charges and r21 is the distance between the charges q1 and q2. The electrostatic force between two charges is not affected by the presence of other charges in the neighbourhood.
Correct
Incorrect
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Question 17 of 90
17. Question
Consider a point charge kept at a point in space. If another point charge is placed at some distance from the first point charge, it experiences either an attractive force or repulsive force. This is called ____
Correct
Consider a point charge kept at a point in space. If another point charge is placed at some distance from the first point charge, it experiences either an attractive force or repulsive force. This is called ‘action at a distance’.
Incorrect
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Question 18 of 90
18. Question
Who introduced the concept of field?
Correct
Michael Faraday introduced the concept of field.
Incorrect
Michael Faraday introduced the concept of field.
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Question 19 of 90
19. Question
Which among the following statement is correct
- According to Faraday, every charge in the universe creates an electric field in the surrounding space, and if another charge is brought into its field, it will interact with the electric field at that point and will experience a force. It may be recalled that the interaction of two masses is similarly explained using the concept of gravitational field.
- Both the electric and gravitational forces are contact forces, hence the field concept is required to explain action at a distance. Consider a source point charge q located at a point in space. Another point charge qo (test charge) is placed at some point P which is at a distance r from the charge q.
- The electrostatic force experienced by the charge qo due to q is given by Coulomb’s law. F = r, where K = The charge q creates an electric field in the surrounding space within which its effect can be felt by another charge. It is measured in terms of a quantity called electric field intensity or simply called electric field E.
Correct
Both the electric and gravitational forces are non-contact forces, hence the field concept is required to explain action at a distance. Consider a source point charge q located at a point in space. Another point charge qo (test charge) is placed at some point P which is at a distance r from the charge q.
Incorrect
Both the electric and gravitational forces are non-contact forces, hence the field concept is required to explain action at a distance. Consider a source point charge q located at a point in space. Another point charge qo (test charge) is placed at some point P which is at a distance r from the charge q.
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Question 20 of 90
20. Question
Correct
The electric field at the point P at a distance r from the point charge q is defined as the force that would be experienced by a unit positive charge placed at that point P and is given by A
Incorrect
The electric field at the point P at a distance r from the point charge q is defined as the force that would be experienced by a unit positive charge placed at that point P and is given by A
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Question 21 of 90
21. Question
Which among the following statement is correct regarding electric field?
- If the charge q is positive then the electric field points away from the source charge and if q is negative, the electric field points towards the source charge q. If the electric field at a point P is r E, then the force experienced by the test charge qo placed at the point P is F = q0
- The equation E = r implies that the electric field is independent of the test charge qo and it depends only on the source charge q. Since the electric field is a vector quantity, at every point in space, this field has unique direction and magnitude.
- In the definition of electric field, it is assumed that the test charge q0 is taken sufficiently small, so that bringing this test charge will not move the source charge. In other words, the test charge is made sufficiently small such that it will not modify the electric field of the source charge.
Correct
Incorrect
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Question 22 of 90
22. Question
How many kinds of electric field are there?
Correct
There are two kinds of the electric field: uniform (constant) electric field and non-uniform electric field. Uniform electric field will have the same direction and constant magnitude at all points in space. Non-uniform electric field will have different directions or different magnitudes or both at different points in space.
Incorrect
There are two kinds of the electric field: uniform (constant) electric field and non-uniform electric field. Uniform electric field will have the same direction and constant magnitude at all points in space. Non-uniform electric field will have different directions or different magnitudes or both at different points in space.
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Question 23 of 90
23. Question
The electric field at an arbitrary point due to a collection of point charges is simply equal to the vector sum of the electric fields created by the individual point charges. This is called ____
Correct
Suppose a number of point charges are distributed in space. To find the electric field at some point P due to this collection of point charges, superposition principle is used. The electric field at an arbitrary point due to a collection of point charges is simply equal to the vector sum of the electric fields created by the individual point charges. This is called superposition of electric fields.
Incorrect
Suppose a number of point charges are distributed in space. To find the electric field at some point P due to this collection of point charges, superposition principle is used. The electric field at an arbitrary point due to a collection of point charges is simply equal to the vector sum of the electric fields created by the individual point charges. This is called superposition of electric fields.
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Question 24 of 90
24. Question
Which among the following statement is correct regarding Electric field due to continuous charge distribution?
- The electric charge is quantized microscopically. While dealing with the electric field due to a charged sphere or a charged wire etc., it is very difficult to look at individual charges in these charged bodies.
- Therefore, it is assumed that charge is distributed continuously on the charged bodies and the discrete nature of charges is not considered here. The electric field due to such continuous charge distributions is found by invoking the method of calculus.
Correct
Incorrect
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Question 25 of 90
25. Question
Which among the following statement is correct
- Electric field vectors are visualized by the concept of electric field lines. They form a set of continuous lines which are the visual representation of the electric field in some region of space. The following rules are followed while drawing electric field lines for charges.
- The electric field lines start from a positive charge and end at negative charges or at infinity. For a positive point charge the electric field lines point radially outward and for a negative point charge, the electric field lines point radially inward.
- Note that for an isolated negative point charge the electric field line starts from the charge and ends only at infinity. For an isolated positive point charge the electric field lines start at infinity and end at the negative charge.
Correct
Note that for an isolated positive point charge the electric field line starts from the charge and ends only at infinity. For an isolated negative point charge the electric field lines start at infinity and end at the negative charge. The electric field vector at a point in space is tangential to the electric field line at that point.
Incorrect
Note that for an isolated positive point charge the electric field line starts from the charge and ends only at infinity. For an isolated negative point charge the electric field lines start at infinity and end at the negative charge. The electric field vector at a point in space is tangential to the electric field line at that point.
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Question 26 of 90
26. Question
Which among the following statement is correct regarding electric field lines?
- The electric field lines are denser (more closer) in a region where the electric field has small magnitude and high dense in a region where the electric field is of large magnitude. In other words, the number of lines passing through a given surface area perpendicular to the lines is proportional to the magnitude of the electric field in that region.
- The magnitude of the electric field for a point charge decreases as the distance increases {|E| ∝ }. So the electric field has greater magnitude at the surface A than at B. Therefore, the number of lines crossing the surface A is greater than the number of lines crossing the surface B. Note that at surface B the electric field lines are farther apart compared to the electric field lines at the surface A.
- No two electric field lines intersect each other. If two lines cross at a point, then there will be two different electric field vectors at the same point. As a consequence, if some charge is placed in the intersection point, then it has to move in two different directions at the same time, which is physically impossible. Hence, electric field lines do not intersect.
Correct
The electric field lines are denser (more closer) in a region where the electric field has larger magnitude and less dense in a region where the electric field is of smaller magnitude. In other words, the number of lines passing through a given surface area perpendicular to the lines is proportional to the magnitude of the electric field.
Incorrect
The electric field lines are denser (more closer) in a region where the electric field has larger magnitude and less dense in a region where the electric field is of smaller magnitude. In other words, the number of lines passing through a given surface area perpendicular to the lines is proportional to the magnitude of the electric field.
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Question 27 of 90
27. Question
Two equal and opposite charges separated by a small distance constitute an _____
Correct
Two equal and opposite charges separated by a small distance constitute an electric dipole. In many molecules, the centres of positive and negative charge do not coincide. Such molecules behave as permanent dipoles. Examples: CO, water, ammonia, HCl etc.
Incorrect
Two equal and opposite charges separated by a small distance constitute an electric dipole. In many molecules, the centres of positive and negative charge do not coincide. Such molecules behave as permanent dipoles. Examples: CO, water, ammonia, HCl etc.
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Question 28 of 90
28. Question
Which among the following statement is correct
- Consider two equal and opposite point charges (+q, –q) that are separated by a distance 2a. The electric dipole moment is defined as p = qr+ + (−q) r_. where r+ is the position vector of +q from the origin and r r_ is the position vector of –q from the origin.
- The electric dipole moment vector lies perpendicular to the line joining two charges and is directed from +q to ̶ The electric field lines for an electric dipole. For simplicity, the two charges are placed on the y-axis. If the two charges are placed on x or z-axis, dipole moment will point from –q to +q.
- The magnitude of the electric dipole moment is equal to the product of the magnitude of one of the charges and the distance between them, |p| = 2qa. Though the electric dipole moment for two equal and opposite charges is defined, it is possible to define and calculate the electric dipole moment for a collection of point charges. The electric dipole moment for a collection of n point charges is given by p = .
Correct
The electric dipole moment vector lies along the line joining two charges and is directed from –q to +q. The electric field lines for an electric dipole. For simplicity, the two charges are placed on the x-axis. Even if the two charges are placed on y or z-axis, dipole moment will point from –q to +q.
Incorrect
The electric dipole moment vector lies along the line joining two charges and is directed from –q to +q. The electric field lines for an electric dipole. For simplicity, the two charges are placed on the x-axis. Even if the two charges are placed on y or z-axis, dipole moment will point from –q to +q.
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Question 29 of 90
29. Question
What is the S.I. unit of dipole moment?
Correct
The SI unit of dipole moment is coulomb metre (Cm).
Incorrect
The SI unit of dipole moment is coulomb metre (Cm).
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Question 30 of 90
30. Question
Which among the following statement is correct regarding Torque experienced by an electric dipole in the uniform electric field?
- Consider an electric dipole of dipole moment p placed in a uniform electric field E whose field lines are equally spaced and point in the same direction. The charge +q will experience a force q E in the direction of the field and charge –q will experience a force –q E in a direction opposite to the field.
- Since the external field E is uniform, the total force acting on the dipole is zero. These two forces acting at different points will constitute a couple and the dipole experience a torque. This torque tends to rotate the dipole. The total torque on the dipole about the point O
- Using right-hand corkscrew rule, it is found that total torque is perpendicular to the plane of the paper and is directed into it. The magnitude of the total torque τ = qE.2a sin θ. where θ is the angle made by r p with r E . Since p = 2aq, the torque is written in terms of the vector product as τ = pE sin θ and is maximum when θ = 90o.
Correct
Incorrect
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Question 31 of 90
31. Question
A sample of HCl gas is placed in a uniform electric field of magnitude 3 × 104 N C–1. The dipole moment of each HCl molecule is 3.4 × 10–30 Cm. Calculate the maximum torque experienced by each HCl molecule?
- τmax = 8.19 × 10−26 Nm
- τmax = 10.2 × 10−26 Nm
- τmax = 12.7 × 10−26 Nm
- τmax = 15.6 × 10−26 Nm
Correct
The maximum torque experienced by the dipole is when it is aligned perpendicular to the applied field
τmax = pE sin900 = 3.4 × 10-30 × 3 × 104
τmax = 10.2 × 10-26 Nm.
Incorrect
The maximum torque experienced by the dipole is when it is aligned perpendicular to the applied field
τmax = pE sin900 = 3.4 × 10-30 × 3 × 104
τmax = 10.2 × 10-26 Nm.
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Question 32 of 90
32. Question
Which among the following is not the conservative forces?
Correct
In mechanics, potential energy is defined for conservative forces. Since gravitational force is a conservative force, its gravitational potential energy. Since Coulomb force is an inversesquare-law force, its also a conservative force like gravitational force. Therefore, we can define potential energy for charge configurations.
Incorrect
In mechanics, potential energy is defined for conservative forces. Since gravitational force is a conservative force, its gravitational potential energy. Since Coulomb force is an inversesquare-law force, its also a conservative force like gravitational force. Therefore, we can define potential energy for charge configurations.
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Question 33 of 90
33. Question
Which among the following statement is correct
- Consider a positive charge q kept fixed at the origin which produces an electric field r E around it. A positive test charge q′ is brought from point R to point P against the repulsive force between q and q′. Work must be done to overcome the repulsion between the charges and this work done is stored as potential energy of the system.
- The test charge q′ is brought from R to P with constant velocity which means that external force used to bring the test charge q′ from R to P must be equal and opposite to the coulomb force (Fext = ̶ Fcoulomb) . The work done is W = .dr.
- Since coulomb force is conservative, work done is dependent of the path and it is independent of on the initial and final positions of the test charge. If potential energy associated with q′ at P is UP and that at R is UR, then difference in potential energy is defined as the work done to bring a test charge q′ from point R to P and is given as UP × UR = W = ΔU.
Correct
Since coulomb force is conservative, work done is independent of the path and it depends only on the initial and final positions of the test charge. If potential energy associated with q′ at P is UP and that at R is UR, then difference in potential energy is defined as the work done to bring a test charge q′ from point R to P and is given as UP – UR = W = ΔU.
Incorrect
Since coulomb force is conservative, work done is independent of the path and it depends only on the initial and final positions of the test charge. If potential energy associated with q′ at P is UP and that at R is UR, then difference in potential energy is defined as the work done to bring a test charge q′ from point R to P and is given as UP – UR = W = ΔU.
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Question 34 of 90
34. Question
Correct
The electric potential at a point P is equal to the work done by an external force to bring a unit positive charge with constant velocity from infinity to the point P in the region of the external electric field E. Mathematically this is written as VP = . The electric potential energy difference can be written as ∆U = q′ ∆V. P
Incorrect
The electric potential at a point P is equal to the work done by an external force to bring a unit positive charge with constant velocity from infinity to the point P in the region of the external electric field E. Mathematically this is written as VP = . The electric potential energy difference can be written as ∆U = q′ ∆V. P
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Question 35 of 90
35. Question
Correct
In the case of gravitational force, mass moves from a point of higher gravitational potential to a point of lower gravitational potential. Similarly, a positive charge moves from a point of higher electrostatic potential to a point of lower electrostatic potential. However, a negative charge moves from lower electrostatic potential to higher electrostatic potential.
Incorrect
In the case of gravitational force, mass moves from a point of higher gravitational potential to a point of lower gravitational potential. Similarly, a positive charge moves from a point of higher electrostatic potential to a point of lower electrostatic potential. However, a negative charge moves from lower electrostatic potential to higher electrostatic potential.
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Question 36 of 90
36. Question
What is the S.I unit of electric field?
Correct
The electric field is a vector quantity and its SI unit is newton per coulomb (NC–1).
Incorrect
The electric field is a vector quantity and its SI unit is newton per coulomb (NC–1).
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Question 37 of 90
37. Question
Which among the following statement is correct regarding Electrostatic potential at a point due to an electric dipole?
Correct
Incorrect
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Question 38 of 90
38. Question
Which among the following statement is correct regarding Equi-potential Surface?
- Consider a point charge q located at some point in space and an imaginary sphere of radius r is chosen by keeping the charge q at its centre. The electric potential at all points on the surface of the given sphere is the same. Such a surface is called an equipotential surface.
- An equipotential surface is a surface on which all the points are at the different electric potential. For a point charge the equipotential surfaces are concentric spherical surfaces. Each spherical surface is an equipotential surface but the value of the potential is same for different spherical surfaces.
- For a uniform electric field, the equipotential surfaces form a set of planes normal to the electric field E. The work done to move a charge q between any two points A and B, W = q (VB – VA). If the points A and B lie on the same equipotential surface, work done is zero because VA = VB.
Correct
An equipotential surface is a surface on which all the points are at the same electric potential. For a point charge the equipotential surfaces are concentric spherical surfaces. Each spherical surface is an equipotential surface but the value of the potential is different for different spherical surfaces. The electric field is normal to an equipotential surface. If it is not normal, then there is a component of the field parallel to the surface.
Incorrect
An equipotential surface is a surface on which all the points are at the same electric potential. For a point charge the equipotential surfaces are concentric spherical surfaces. Each spherical surface is an equipotential surface but the value of the potential is different for different spherical surfaces. The electric field is normal to an equipotential surface. If it is not normal, then there is a component of the field parallel to the surface.
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Question 39 of 90
39. Question
Correct
Consider a positive charge q kept fixed at the origin. To move a unit positive charge by a small distance dx towards q in the electric field E, the work done is given by dW = −E dx. The minus sign implies that work is done against the electric field. This work done is equal to electric potential difference. Therefore, E = .
Incorrect
Consider a positive charge q kept fixed at the origin. To move a unit positive charge by a small distance dx towards q in the electric field E, the work done is given by dW = −E dx. The minus sign implies that work is done against the electric field. This work done is equal to electric potential difference. Therefore, E = .
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Question 40 of 90
40. Question
Correct
The electric potential at a point at a distance r from point charge q1 is given by V = . This potential V is the work done to bring a unit positive charge from infinity to the point. Now if the charge q2 is brought from infinity to that point at a distance r from q1, the work done is the product of q2 and the electric potential at that point. Thus, we have W = q2 V.
Incorrect
The electric potential at a point at a distance r from point charge q1 is given by V = . This potential V is the work done to bring a unit positive charge from infinity to the point. Now if the charge q2 is brought from infinity to that point at a distance r from q1, the work done is the product of q2 and the electric potential at that point. Thus, we have W = q2 V.
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Question 41 of 90
41. Question
Which among the following work on the principle of torque acting on an electric dipole?
Correct
Microwave oven works on the principle of torque acting on an electric dipole. The food we consume has water molecules which are permanent electric dipoles. Oven produces microwaves that are oscillating electromagnetic fields and produce torque on the water molecules.
Incorrect
Microwave oven works on the principle of torque acting on an electric dipole. The food we consume has water molecules which are permanent electric dipoles. Oven produces microwaves that are oscillating electromagnetic fields and produce torque on the water molecules.
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Question 42 of 90
42. Question
Correct
In addition to p and E, the potential energy also depends on the orientation θ of the electric dipole with respect to the external electric field. The potential energy is maximum when the dipole is aligned anti-parallel (θ = π) to the external electric field and minimum when the dipole is aligned parallel (θ = 0) to the external electric field.
Incorrect
In addition to p and E, the potential energy also depends on the orientation θ of the electric dipole with respect to the external electric field. The potential energy is maximum when the dipole is aligned anti-parallel (θ = π) to the external electric field and minimum when the dipole is aligned parallel (θ = 0) to the external electric field.
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Question 43 of 90
43. Question
The number of electric field lines crossing a given area kept normal to the electric field lines is called _____
Correct
The number of electric field lines crossing a given area kept normal to the electric field lines is called electric flux.
Incorrect
The number of electric field lines crossing a given area kept normal to the electric field lines is called electric flux.
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Question 44 of 90
44. Question
Electric flux is usually denoted by the Greek letter ____
Correct
Electric flus is usually denoted by the Greek letter ΦE.
Incorrect
Electric flus is usually denoted by the Greek letter ΦE.
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Question 45 of 90
45. Question
Which among the following statement is correct
- The electric field of a point charge is drawn in this figure. Consider two small rectangular area elements placed normal to the field at regions A and B. Even though these elements have the same area, the number of electric field lines crossing the element in region A is more than that crossing the element in region B.
- Therefore, the electric flux in region A is more than that in region B. Since electric field strength for a point charge decreases as the distance increases, electric flux also decreases as the distance increases. The above discussion gives a qualitative idea of electric flux. However, a precise definition of electric flux is needed.
Correct
Incorrect
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Question 46 of 90
46. Question
What is the unit of Electric flux?
- N m C
- N m C2
- N m2 C ̶ 1
- N m-2 C-1
Correct
The unit of Electric flux N m2 C–1. Electric flux is a scalar quantity and it can be positive or negative.
Incorrect
The unit of Electric flux N m2 C–1. Electric flux is a scalar quantity and it can be positive or negative.
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Question 47 of 90
47. Question
Which among the following statement is correct regarding Electric flux for uniform Electric field?
- Consider a uniform electric field in a region of space. Let us choose an area A normal to the electric field lines. The electric flux for this case is ΦE = EA. Suppose the same area A is kept parallel to the uniform electric field, then no electric field lines pass through the area A ,. The electric flux for this case is zero. ΦE = 0
- If the area is inclined at an angle θ with the field, then the component of the electric field perpendicular to the area alone contributes to the electric flux. The electric field component parallel to the surface area will not contribute to the electric flux. For this case, the electric flux. ΦE = (E cosθ) A.
- Further, θ is also the angle between the electric flux and the direction normal to the area. Hence in general, for uniform electric field, the electric flux is defined as ΦE = E A = EA cosθ. If θ = 90o. Therefore ΦE = E A cos900 = E A
Correct
Further, θ is also the angle between the electric field and the direction normal to the area. Hence in general, for uniform electric field, the electric flux is defined as ΦE = ⋅ E A = EA cosθ. If θ = 90o. Therefore, ΦE = ⋅ E A = 0.
Incorrect
Further, θ is also the angle between the electric field and the direction normal to the area. Hence in general, for uniform electric field, the electric flux is defined as ΦE = ⋅ E A = EA cosθ. If θ = 90o. Therefore, ΦE = ⋅ E A = 0.
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Question 48 of 90
48. Question
The total electric flux over the closed surface is written as _____
Correct
The total electric flux over this closed surface is written as ΦE = . The total electric flux over a closed surface can be negative, positive or zero.
Incorrect
The total electric flux over this closed surface is written as ΦE = . The total electric flux over a closed surface can be negative, positive or zero.
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Question 49 of 90
49. Question
In general, the electric flux is negative if the electric field lines _____
Correct
In general, the electric flux is negative if the electric field lines enter the closed surface and positive if the electric field lines leave the closed surface.
Incorrect
In general, the electric flux is negative if the electric field lines enter the closed surface and positive if the electric field lines leave the closed surface.
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Question 50 of 90
50. Question
Correct
Gauss’s law states that if a charge Q is enclosed by an arbitrary closed surface, then the total electric flux ΦE through the closed surface is ΦE = = .
Incorrect
Gauss’s law states that if a charge Q is enclosed by an arbitrary closed surface, then the total electric flux ΦE through the closed surface is ΦE = = .
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Question 51 of 90
51. Question
Correct
The electric field is spherically symmetric for a point charge, therefore spherical Gaussian surface is chosen. Cylindrical and planar Gaussian surfaces can be chosen for other kinds of charge configurations. The electric field E is due to charges present inside and outside the Gaussian surface but the charge Qencl denotes the charges which lie only inside the Gaussian surface.
Incorrect
The electric field is spherically symmetric for a point charge, therefore spherical Gaussian surface is chosen. Cylindrical and planar Gaussian surfaces can be chosen for other kinds of charge configurations. The electric field E is due to charges present inside and outside the Gaussian surface but the charge Qencl denotes the charges which lie only inside the Gaussian surface.
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Question 52 of 90
52. Question
Electric field due to any arbitrary charge configuration cannot be calculated using which among the following law?
Correct
Electric field due to any arbitrary charge configuration can be calculated using Coulomb’s law or Gauss law. If the charge configuration possesses some kind of symmetry, then Gauss law is a very efficient way to calculate the electric field.
Incorrect
Electric field due to any arbitrary charge configuration can be calculated using Coulomb’s law or Gauss law. If the charge configuration possesses some kind of symmetry, then Gauss law is a very efficient way to calculate the electric field.
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Question 53 of 90
53. Question
Correct
Incorrect
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Question 54 of 90
54. Question
Correct
At the points P2 and P3 , the electric field due to both plates are equal in magnitude and opposite in direction. As a result, electric field at a point outside the plates is zero. But between the plates, electric fields are in the same direction i.e., towards the right and the total electric field at a point P1 is Einside = + = .
Incorrect
At the points P2 and P3 , the electric field due to both plates are equal in magnitude and opposite in direction. As a result, electric field at a point outside the plates is zero. But between the plates, electric fields are in the same direction i.e., towards the right and the total electric field at a point P1 is Einside = + = .
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Question 55 of 90
55. Question
Gauss law is a powerful technique whenever a given charge configuration possesses ____
Correct
Gauss law is a powerful technique whenever a given charge configuration possesses spherical, cylindrical or planar symmetry, then the electric field due to such a charge configuration can be easily found. If there is no such symmetry, the direct method (Coulomb’s law and calculus) can be used. For example, it is difficult to use Gauss law to find the electric field for a dipole since it has no spherical, cylindrical or planar symmetry.
Incorrect
Gauss law is a powerful technique whenever a given charge configuration possesses spherical, cylindrical or planar symmetry, then the electric field due to such a charge configuration can be easily found. If there is no such symmetry, the direct method (Coulomb’s law and calculus) can be used. For example, it is difficult to use Gauss law to find the electric field for a dipole since it has no spherical, cylindrical or planar symmetry.
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Question 56 of 90
56. Question
Which among the following statement is correct
- An electrical conductor has a minimum number of mobile charges which are free to move in the material. In a metallic conductor, these mobile charges are free electrons which are bound to many atoms and therefore are restricted to move on the surface of the conductor.
- When there is no external electric field, the free electrons are in continuous random motion in all directions. As a result, there is no net motion of electrons along any particular direction which implies that the conductor is in electrostatic equilibrium. Thus, at electrostatic equilibrium, there is no net current in the conductor.
Correct
An electrical conductor has a large number of mobile charges which are free to move in the material. In a metallic conductor, these mobile charges are free electrons which are not bound to any atom and therefore are free to move on the surface of the conductor.
Incorrect
An electrical conductor has a large number of mobile charges which are free to move in the material. In a metallic conductor, these mobile charges are free electrons which are not bound to any atom and therefore are free to move on the surface of the conductor.
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Question 57 of 90
57. Question
Which among the following statement is correct
- The electric field is zero everywhere inside the conductor. This is true regardless of whether the conductor is solid or hollow. This is an experimental fact. Suppose the electric field is not zero inside the metal, then there will be a force on the mobile charge carriers due to this electric field.
- As a result, there will be a net motion of the mobile charges, which contradicts the conductors being in electrostatic equilibrium. Thus the electric field is zero everywhere inside the conductor. We can also understand this fact by applying an external uniform electric field on the conductor. Before applying the external electric field, the free electrons in the conductor are uniformly distributed in the conductor.
- When an electric field is applied, the free electrons accelerate to the right causing the right plate to be negatively charged and the left plate to be positively charged Due to this realignment of free electrons, there will be an internal electric field created inside the conductor which decrease until it nullifies the external electric field. Once the external electric field is nullified the conductor is said to be in electrostatic equilibrium.
Correct
When an electric field is applied, the free electrons accelerate to the left causing the left plate to be negatively charged and the right plate to be positively charged. Due to this realignment of free electrons, there will be an internal electric field created inside the conductor which increases until it nullifies the external electric field. Once the external electric field is nullified the conductor is said to be in electrostatic equilibrium.
Incorrect
When an electric field is applied, the free electrons accelerate to the left causing the left plate to be negatively charged and the right plate to be positively charged. Due to this realignment of free electrons, there will be an internal electric field created inside the conductor which increases until it nullifies the external electric field. Once the external electric field is nullified the conductor is said to be in electrostatic equilibrium.
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Question 58 of 90
58. Question
Which among the following statement is correct
- There is more net charge inside the conductors. The charges must reside on both the surface of the conductors. We can prove this property using Gauss law. Consider an arbitrarily shaped conductor. A Gaussian surface is drawn inside the conductor such that it is very close to the surface of the conductor.
- Since the electric field is zero everywhere inside the conductor, the net electric flux is also zero over this Gaussian surface. From Gauss’s law, this implies that there is no net charge inside the conductor. Even if some charge is introduced inside the conductor, it immediately reaches the surface of the conductor.
Correct
There is no net charge inside the conductors. The charges must reside only on the surface of the conductors. We can prove this property using Gauss law. Consider an arbitrarily shaped conductor. A Gaussian surface is drawn inside the conductor such that it is very close to the surface of the conductor.
Incorrect
There is no net charge inside the conductors. The charges must reside only on the surface of the conductors. We can prove this property using Gauss law. Consider an arbitrarily shaped conductor. A Gaussian surface is drawn inside the conductor such that it is very close to the surface of the conductor.
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Question 59 of 90
59. Question
Correct
This means that the conductor is not in equilibrium. Therefore, at electrostatic equilibrium, the electric field must be perpendicular to the surface of the conductor. We now prove that the electric field has magnitude σ / just outside the conductor’s surface. Consider a small cylindrical Gaussian surface. One half of this cylinder is embedded inside the conductor.
Incorrect
This means that the conductor is not in equilibrium. Therefore, at electrostatic equilibrium, the electric field must be perpendicular to the surface of the conductor. We now prove that the electric field has magnitude σ / just outside the conductor’s surface. Consider a small cylindrical Gaussian surface. One half of this cylinder is embedded inside the conductor.
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Question 60 of 90
60. Question
Which among the following statement is correct
- The electrostatic potential has the same value on the surface and inside of the conductor. We know that the conductor has no parallel electric component on the surface which means that charges can be moved on the surface without doing any work.
- This is possible only if the electrostatic potential is constant at end points on the surface and there is potential difference between any two points on the surface. Since the electric field is zero inside the conductor, the potential is maximum at the surface of the conductor. Thus, at electrostatic equilibrium, the conductor is always at equipotential.
Correct
This is possible only if the electrostatic potential is constant at all points on the surface and there is no potential difference between any two points on the surface. Since the electric field is zero inside the conductor, the potential is the same as the surface of the conductor. Thus, at electrostatic equilibrium, the conductor is always at equipotential.
Incorrect
This is possible only if the electrostatic potential is constant at all points on the surface and there is no potential difference between any two points on the surface. Since the electric field is zero inside the conductor, the potential is the same as the surface of the conductor. Thus, at electrostatic equilibrium, the conductor is always at equipotential.
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Question 61 of 90
61. Question
Charging a conductor without actual contact is called _____
Correct
Whenever a charged rod is touched by another conductor, charges start to flow from charged rod to the conductor. Is it possible to charge a conductor without any contact? yes. This type of charging a conductor without actual contact is called electrostatic induction.
Incorrect
Whenever a charged rod is touched by another conductor, charges start to flow from charged rod to the conductor. Is it possible to charge a conductor without any contact? yes. This type of charging a conductor without actual contact is called electrostatic induction.
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Question 62 of 90
62. Question
Which among the following statement is correct regarding electrostatic induction
- Consider an uncharged (neutral) conducting sphere at rest on an insulating stand. Suppose a negatively charged rod is brought near the conductor without touching it. The negative charge of the rod repels the electrons in the conductor to the opposite side. As a result, positive charges are induced near the region of the charged rod while negative charges on the farther side.
- Before introducing the charged rod, the free electrons were distributed uniformly on the surface of the conductor and the net charge is zero. Once the charged rod is brought near the conductor, the distribution is no longer uniform with more electrons located on the farther side of the rod and positive charges are located closer to the rod. But the total charge is zero.
- Now the conducting sphere is connected to the ground through a conducting wire that removes the electron from the conducting sphere. Note that positive charges will not flow to the ground because they are attracted by the negative charges of the rod. When the grounding wire is removed from the conductor, the positive charges remain near the charged rod. Now the positive charge gets distributed uniformly on the surface of the conductor By this process, the neutral conducting sphere becomes positively charged.
Correct
Incorrect
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Question 63 of 90
63. Question
A sensitive electrical instrument which is to be protected from external electrical disturbance can be kept inside this cavity. This is called _____
Correct
Consider a cavity inside the conductor. Whatever be the charges at the surfaces and whatever be the electrical disturbances outside, the electric field inside the cavity is zero. A sensitive electrical instrument which is to be protected from external electrical disturbance can be kept inside this cavity. This is called electrostatic shielding.
Incorrect
Consider a cavity inside the conductor. Whatever be the charges at the surfaces and whatever be the electrical disturbances outside, the electric field inside the cavity is zero. A sensitive electrical instrument which is to be protected from external electrical disturbance can be kept inside this cavity. This is called electrostatic shielding.
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Question 64 of 90
64. Question
Which is an instrument used to demonstrate Electrostatic shielding?
Correct
Faraday cage is an instrument used to demonstrate Electrostatic shielding. It is made up of metal bars. If an artificial lightning jolt is created outside, the person inside is not affected. During lightning accompanied by a thunderstorm, it is always safer to sit inside a bus than in open ground or under a tree. The metal body of the bus provides electrostatic shielding, since the electric field inside is zero.
Incorrect
Faraday cage is an instrument used to demonstrate Electrostatic shielding. It is made up of metal bars. If an artificial lightning jolt is created outside, the person inside is not affected. During lightning accompanied by a thunderstorm, it is always safer to sit inside a bus than in open ground or under a tree. The metal body of the bus provides electrostatic shielding, since the electric field inside is zero.
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Question 65 of 90
65. Question
Which is a non-conducting material and has no free electrons?
Correct
A dielectric is a non-conducting material and has no free electrons. The electrons in a dielectric are bound within the atoms.
Incorrect
A dielectric is a non-conducting material and has no free electrons. The electrons in a dielectric are bound within the atoms.
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Question 66 of 90
66. Question
Which among the following is not the example of dielectrics?
Correct
Ebonite, glass and mica are some examples of dielectrics. When an external electric field is applied, the electrons are not free to move anywhere but they are realigned in a specific way. A dielectric is made up of either polar molecules or non-polar molecules.
Incorrect
Ebonite, glass and mica are some examples of dielectrics. When an external electric field is applied, the electrons are not free to move anywhere but they are realigned in a specific way. A dielectric is made up of either polar molecules or non-polar molecules.
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Question 67 of 90
67. Question
Which is one in which centres of positive and negative charges coincide?
Correct
A non-polar molecule is one in which centres of positive and negative charges coincide. As a result, it has no permanent dipole moment. When an external electric field is applied, the centres of positive and negative charges are separated by a small distance which induces dipole moment in the direction of the external electric field. Then the dielectric is said to be polarized by an external electric field.
Incorrect
A non-polar molecule is one in which centres of positive and negative charges coincide. As a result, it has no permanent dipole moment. When an external electric field is applied, the centres of positive and negative charges are separated by a small distance which induces dipole moment in the direction of the external electric field. Then the dielectric is said to be polarized by an external electric field.
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Question 68 of 90
68. Question
Which among the following is not the example of Non-polar molecule?
- H2
- O2
- HCL
- None of the above
Correct
Examples of non-polar molecules are hydrogen (H2 ), oxygen (O2 ), and carbon dioxide (CO2 ) etc.
Incorrect
Examples of non-polar molecules are hydrogen (H2 ), oxygen (O2 ), and carbon dioxide (CO2 ) etc.
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Question 69 of 90
69. Question
Which among the following is not the example of Polar molecule?
- H2O
- N2O
- NH3
- None of the above
Correct
Examples of polar molecules are H2 O, N2 O, HCl, NH3.
Incorrect
Examples of polar molecules are H2 O, N2 O, HCl, NH3.
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Question 70 of 90
70. Question
Which among the following statement is correct regarding polar molecules?
- In polar molecules, the centres of the positive and negative charges are separated even in the absence of an external electric field. They have a permanent dipole moment. Due to thermal motion, the direction of each dipole moment is oriented randomly.
- Hence the net dipole moment is maximum in the absence of an external electric field. When an external electric field is applied, the dipoles inside the material tend to align in the opposite direction of the electric field. Hence a net dipole moment is induced in it. Then the dielectric is said to be polarized by an external electric field.
Correct
Hence the net dipole moment is zero in the absence of an external electric field. When an external electric field is applied, the dipoles inside the material tend to align in the direction of the electric field. Hence a net dipole moment is induced in it. Then the dielectric is said to be polarized by an external electric field.
Incorrect
Hence the net dipole moment is zero in the absence of an external electric field. When an external electric field is applied, the dipoles inside the material tend to align in the direction of the electric field. Hence a net dipole moment is induced in it. Then the dielectric is said to be polarized by an external electric field.
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Question 71 of 90
71. Question
Which is defined as the total dipole moment per unit volume of the dielectric?
Correct
In the presence of an external electric field, the dipole moment is induced in the dielectric material. Polarisation r P is defined as the total dipole moment per unit volume of the dielectric. For most dielectrics (linear isotropic), the Polarisation is directly proportional to the strength of the external electric field. P = XeEext.
Incorrect
In the presence of an external electric field, the dipole moment is induced in the dielectric material. Polarisation r P is defined as the total dipole moment per unit volume of the dielectric. For most dielectrics (linear isotropic), the Polarisation is directly proportional to the strength of the external electric field. P = XeEext.
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Question 72 of 90
72. Question
In P = Xe Eext, Xe is a constant called _____
Correct
In P = Xe Eext, Xe is a constant called the electric susceptibility which is a characteristic of each dielectric.
Incorrect
In P = Xe Eext, Xe is a constant called the electric susceptibility which is a characteristic of each dielectric.
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Question 73 of 90
73. Question
Which among the following statement is correct regarding Induced Electric field inside the dielectric?
- When an external electric field is applied on a conductor, the charges are aligned in such a way that an internal electric field is created which tends to cancel the external electric field. But in the case of a dielectric, which has no free electrons, the external electric field only realigns the charges so that an internal electric field is produced.
- The magnitude of the internal electric field is smaller than that of external electric field. Therefore, the net electric field inside the dielectric is not zero but is parallel to an external electric field with magnitude less than that of the external electric field. For example, let us consider a rectangular dielectric slab placed between two oppositely charged plates.
- The uniform electric field between the plates acts as an external electric field Eext which polarizes the dielectric placed between plates. The positive charges are induced on one side surface and negative charges are induced on the other side of surface. But inside the dielectric, the net charge is zero even in a small volume.
Correct
Incorrect
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Question 74 of 90
74. Question
When the external electric field applied to a dielectric is very large, it tears the atoms apart so that the bound charges become free charges. Then the dielectric starts to conduct electricity. This is called _____
Correct
When the external electric field applied to a dielectric is very large, it tears the atoms apart so that the bound charges become free charges. Then the dielectric starts to conduct electricity. This is called dielectric breakdown.
Incorrect
When the external electric field applied to a dielectric is very large, it tears the atoms apart so that the bound charges become free charges. Then the dielectric starts to conduct electricity. This is called dielectric breakdown.
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Question 75 of 90
75. Question
The maximum electric field the dielectric can withstand before it breaks down is called ___
Correct
The maximum electric field the dielectric can withstand before it breaks down is called dielectric strength. For example, the dielectric strength of air is 3 × 106 V m–1. If the applied electric field increases beyond this, a spark is produced in the air.
Incorrect
The maximum electric field the dielectric can withstand before it breaks down is called dielectric strength. For example, the dielectric strength of air is 3 × 106 V m–1. If the applied electric field increases beyond this, a spark is produced in the air.
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Question 76 of 90
76. Question
Which is a device used to store electric charge and electrical energy?
Correct
Capacitor is a device used to store electric charge and electrical energy. It consists of two conducting objects (usually plates or sheets) separated by some distance. Capacitors are widely used in many electronic circuits and have applications in many areas of science and technology.
Incorrect
Capacitor is a device used to store electric charge and electrical energy. It consists of two conducting objects (usually plates or sheets) separated by some distance. Capacitors are widely used in many electronic circuits and have applications in many areas of science and technology.
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Question 77 of 90
77. Question
Which among the following substance has highest Dielectric strength?
Correct
Mica – 100 × 106Vm–1, Teflon – 60 × 106Vm–1, Paper – 16 × 106Vm–1, Air – 3 × 106Vm–1, Pyrex glass – 14 × 106Vm–1.
Incorrect
Mica – 100 × 106Vm–1, Teflon – 60 × 106Vm–1, Paper – 16 × 106Vm–1, Air – 3 × 106Vm–1, Pyrex glass – 14 × 106Vm–1.
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Question 78 of 90
78. Question
Which among the following statement is correct?
- A simple capacitor consists of two parallel metal plates separated by a small distance. When a capacitor is connected to a battery of potential difference V, the electrons are transferred from one plate to the other plate by battery so that one plate becomes negatively charged with a charge of –Q and the other plate positively charged with +Q.
- The potential difference between the plates is equivalent to the battery’s terminal voltage. If the battery voltage is increased, the amount of charges stored in the plates decrease. In general, the charge stored in the capacitor is inverse to the potential difference between the plates. Q = C/V.
- where the C is the proportionality constant called capacitance. The capacitance C of a capacitor is defined as the ratio of the magnitude of charge on either of the conductor plates to the potential difference existing between them. C =Q/V .
Correct
The potential difference between the plates is equivalent to the battery’s terminal voltage. If the battery voltage is increased, the amount of charges stored in the plates also increase. In general, the charge stored in the capacitor is proportional to the potential difference between the plates. Q = C/V.
Incorrect
The potential difference between the plates is equivalent to the battery’s terminal voltage. If the battery voltage is increased, the amount of charges stored in the plates also increase. In general, the charge stored in the capacitor is proportional to the potential difference between the plates. Q = C/V.
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Question 79 of 90
79. Question
What is the S.I unit of capacitance?
Correct
The SI unit of capacitance is coulomb per volt or farad (F) in honour of Michael Faraday. Farad is a larger unit of capacitance. In practice, capacitors are available in the range of microfarad (1µF = 10–6 F) to picofarad (1pF = 10–12 F). Note that the total charge stored in the capacitor is zero (Q – Q = 0). When we say the capacitor stores charges, it means the amount of charge that can be stored in any one of the plates.
Incorrect
The SI unit of capacitance is coulomb per volt or farad (F) in honour of Michael Faraday. Farad is a larger unit of capacitance. In practice, capacitors are available in the range of microfarad (1µF = 10–6 F) to picofarad (1pF = 10–12 F). Note that the total charge stored in the capacitor is zero (Q – Q = 0). When we say the capacitor stores charges, it means the amount of charge that can be stored in any one of the plates.
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Question 80 of 90
80. Question
Which among the following statement is correct regarding Capacitance of a parallel plate capacitor?
Correct
Incorrect
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Question 81 of 90
81. Question
The energy stored per unit volume of space is defined as _____
Correct
The energy stored per unit volume of space is defined as energy density uE = . From equation we get uE = ∈0 E2.
Incorrect
The energy stored per unit volume of space is defined as energy density uE = . From equation we get uE = ∈0 E2.
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Question 82 of 90
82. Question
Correct
Incorrect
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Question 83 of 90
83. Question
Which among the following statement is correct regarding applications of capacitors?
- Flash capacitors are used in digital cameras for taking photographs. The flash which comes from the camera when we take photographs is due to the energy released from the capacitor, called a flash capacitor.
- During cardiac arrest, a device called heart defibrillator is used to give a sudden surge of a large amount of electrical energy to the patient’s chest to retrieve the normal heart function.
- Capacitors are used in the ignition system of automobile engines to increase sparking. Capacitors are used to increase power fluctuations in power supplies and to increase the efficiency of power transmission.
Correct
Capacitors are used in the ignition system of automobile engines to eliminate sparking. Capacitors are used to reduce power fluctuations in power supplies and to increase the efficiency of power transmission. However, capacitors have disadvantage as well. Even after the battery or power supply is removed, the capacitor stores charges and energy for some time.
Incorrect
Capacitors are used in the ignition system of automobile engines to eliminate sparking. Capacitors are used to reduce power fluctuations in power supplies and to increase the efficiency of power transmission. However, capacitors have disadvantage as well. Even after the battery or power supply is removed, the capacitor stores charges and energy for some time.
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Question 84 of 90
84. Question
Which among the following statement is incorrect
- Effect of dielectrics in capacitors when the battery is disconnected charge (Q) is constant, voltage (V), electric field (E) and energy (U) decreases while capacitance (C) increases.
- Effect of dielectrics in capacitors when the battery is connected charge (Q) is constant, voltage (V), electric field (E) and energy (U) increase while capacitance (C) decrease.
Correct
Effect of dielectrics in capacitors when the battery is connected charge (Q) is increased, voltage (V), electric field (E) are constant while capacitance (C) and Energy (U) increase.
Incorrect
Effect of dielectrics in capacitors when the battery is connected charge (Q) is increased, voltage (V), electric field (E) are constant while capacitance (C) and Energy (U) increase.
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Question 85 of 90
85. Question
Which among the following statement is correct regarding Capacitor in series?
- Consider three capacitors of capacitance C1 ,C2 and C3 connected in series with a battery of voltage V. As soon as the battery is connected to the capacitors in series, the electrons of charge –Q are transferred from negative terminal to the right plate of C3 which pushes the electrons of same amount –Q from left plate of C3 to the right plate of C2 due to electrostatic induction.
- Similarly, the left plate of C2 pushes the charges of –Q to the right plate of C1 which induces the positive charge +Q on the left plate of C1. At the same time, electrons of charge –Q are transferred from left plate of C1 to positive terminal of the battery. By these processes, each capacitor stores the same amount of charge Q.
- The capacitances of the capacitors are in general different, so that the voltage across each capacitor is also different and are denoted as V1, V2 and V3 The sum of the voltages across the capacitor must be equal to the voltage of the battery V=V1+V2 + V3. If three capacitors in series are considered to form an equivalent single capacitor Cs, (1/Cs) = (1/C1) + (1/C2) + (1/C3).
Correct
Incorrect
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Question 86 of 90
86. Question
Which among the following statement is correct regarding Capacitance in parallel
- Consider three capacitors of capacitance C1 , C2 and C3 connected in parallel with a battery of voltage V. Since corresponding sides of the capacitors are connected to the same positive and negative terminals of the battery, the voltage across each capacitor is equal to the battery’s voltage. Since capacitances of the capacitors are different the charge stored in each capacitor is not the same.
- Let the charge stored in the three capacitors be Q1 , Q2, and Q3 According to the law of conservation of total charge, the sum of these three charges is equal to the charge Q transferred by the battery, Q = Q1 +Q2 +Q3. Since Q = CV, we have Q = C1 V + C2 V + C3 V.
- If these three capacitors are considered to form a single equivalent capacitance CP which stores the total charge Q, then we can write Q = CP Substituting this in equation we get, 1/ (CP V) = 1/C1V + 1/C2V + 1/C3V. Thus, 1/CP = 1/C1 + 1/C2 + 1/C3. Thus, the equivalent capacitance of capacitors connected in parallel is equal to the sum of the reciprocal of individual capacitances. The equivalent capacitance CP in a parallel connection is always smaller than the largest individual capacitance.
Correct
If these three capacitors are considered to form a single equivalent capacitance CP which stores the total charge Q, then we can write Q = CP V. Substituting this in equation, we get CP V = C1 V + C2 V + C3 V. Thus, CP = C1 + C2 + C3. the equivalent capacitance of capacitors connected in parallel is equal to the sum of the individual capacitances. The equivalent capacitance CP in a parallel connection is always greater than the largest individual capacitance.
Incorrect
If these three capacitors are considered to form a single equivalent capacitance CP which stores the total charge Q, then we can write Q = CP V. Substituting this in equation, we get CP V = C1 V + C2 V + C3 V. Thus, CP = C1 + C2 + C3. the equivalent capacitance of capacitors connected in parallel is equal to the sum of the individual capacitances. The equivalent capacitance CP in a parallel connection is always greater than the largest individual capacitance.
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Question 87 of 90
87. Question
Which among the following statement is correct regarding Distribution of charges in a conductor
- Consider two conducting spheres A and B of radii r1 and r2 respectively connected to each other by a thin conducting wire. The distance between the spheres is much smaller than the radii of either spheres. If a charge Q is introduced into any one of the spheres, this charge Q is redistributed into both the spheres such that the electrostatic potential is different in both the spheres.
- They are now uniformly charged and attain electrostatic equilibrium. Let q1 be the charge residing on the surface of sphere A and q2 is the charge residing on the surface of sphere B such that Q = q1 + q2 . The charges are distributed only on the surface and there is no net charge inside the conductor
- The electrostatic potential at the surface of the sphere A is given by VA = . The electrostatic potential at the surface of the sphere B is given by VB = . The surface of the conductor is an equipotential. Since the spheres are connected by the conducting wire, the surfaces of both the spheres together form an equipotential surface. This implies that VA = VB. we know q = 4πrσ. Thus, σ1 r1 = σ2 r2. from which we conclude that σr = constant
Correct
Consider two conducting spheres A and B of radii r1 and r2 respectively connected to each other by a thin conducting wire. The distance between the spheres is much greater than the radii of either spheres. If a charge Q is introduced into any one of the spheres, this charge Q is redistributed into both the spheres such that the electrostatic potential is same in both the spheres.
Incorrect
Consider two conducting spheres A and B of radii r1 and r2 respectively connected to each other by a thin conducting wire. The distance between the spheres is much greater than the radii of either spheres. If a charge Q is introduced into any one of the spheres, this charge Q is redistributed into both the spheres such that the electrostatic potential is same in both the spheres.
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Question 88 of 90
88. Question
Lightning arrester or lightning conductor works on the principle of ______
Correct
Lightning arrester or lightning conductor is a device used to protect tall buildings from lightning strikes. It works on the principle of action at points or corona discharge.
Incorrect
Lightning arrester or lightning conductor is a device used to protect tall buildings from lightning strikes. It works on the principle of action at points or corona discharge.
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Question 89 of 90
89. Question
Which among the following statement is incorrect regarding Action of points?
- Consider a charged conductor of irregular shape. We know that smaller the radius of curvature, the larger is the charge density. The end of the conductor which has larger curvature (smaller radius) has a large charge accumulation.
- As a result, the electric field near this edge is very low and it deionizes the surrounding air. The positive ions are attracted at the sharp edge and negative ions are repelled towards the sharper edge. This reduces the total charge of the conductor near the sharp edge. This is called action of points or corona discharge.
Correct
As a result, the electric field near this edge is very high and it ionizes the surrounding air. The positive ions are repelled at the sharp edge and negative ions are attracted towards the sharper edge. This reduces the total charge of the conductor near the sharp edge. This is called action of points or corona discharge.
Incorrect
As a result, the electric field near this edge is very high and it ionizes the surrounding air. The positive ions are repelled at the sharp edge and negative ions are attracted towards the sharper edge. This reduces the total charge of the conductor near the sharp edge. This is called action of points or corona discharge.
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Question 90 of 90
90. Question
Who in the year 1929, designed a machine which produces a large amount of electrostatic potential difference, up to several million volts (10-7 V)?
Correct
In the year 1929, Robert Van de Graaff designed a machine which produces a large amount of electrostatic potential difference, up to several million volts (10-7 V). This Van de Graff generator works on the principle of electrostatic induction and action at points. The high voltage produced in this Van de Graaff generator is used to accelerate positive ions (protons and deuterons) for nuclear disintegrations and other applications.0
Incorrect
In the year 1929, Robert Van de Graaff designed a machine which produces a large amount of electrostatic potential difference, up to several million volts (10-7 V). This Van de Graff generator works on the principle of electrostatic induction and action at points. The high voltage produced in this Van de Graaff generator is used to accelerate positive ions (protons and deuterons) for nuclear disintegrations and other applications.0
Leaderboard: Electrostatics Online Test 12th Science
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