Electric Charges and Fields Mock Test – Class 12 Physics

1. In the derivation of the point-charge field using Gauss’s law, the step is valid because

2. A medium has dielectric constant . If the force between two charges in vacuum is , the force between the same charges at the same separation in this medium is

3. A charge distribution is described by the following data.

The mismatched row is

4. A charged metal sphere touches an identical neutral metal sphere and is then separated. The charging process involved here is mainly

5. A graph is plotted between electric field magnitude due to a fixed point charge and . The graph is a straight line through the origin. The slope of this graph is

6. In a collinear charge system, a zero net force point is more likely to occur where

7. A point charge is fixed at the origin. At point , the electric field is . If a charge is placed at , the force on it is

8. A dipole of moment is in a uniform electric field . It rotates slowly from to . The change in potential energy is

9. A dipole is placed in a uniform electric field. At one orientation its torque magnitude is , and its potential energy is negative. The angle between and is

10. Lightning is mentioned in elementary electrostatics mainly as a large-scale example of

11. On the equatorial line of an electric dipole, the exact field magnitude at distance from the centre is

12. A square surface of side has area vector . A uniform field makes with . If the surface is then rotated so that the angle becomes , the change in flux is

13. In the arrangement described below, sphere P has charge , sphere Q has charge , and sphere R has charge . If sphere P is tested separately with Q and then with R, the nature of interaction is

14. Charges and are fixed apart in vacuum. What is the magnitude of the electric field at the midpoint between them? Take .

15. Assertion: Two equal and opposite infinite plane sheets produce a uniform electric field between them and zero field outside in the ideal model.
Reason: Between the sheets the field contributions are in the same direction, while outside they are in opposite directions.

16. A dipole of moment is in a uniform field . The work required by an external agent to rotate it slowly from stable equilibrium to unstable equilibrium is

17. Study the table and identify the row that violates charge quantisation for an isolated body. Take as the elementary charge.

18. A statement says, “A dielectric medium increases the Coulomb force because is placed in the formula.” The suitable correction is that the medium

19. A calculation uses . This is equivalent to using

20. A graph is plotted between Coulomb force magnitude and for two fixed point charges in vacuum. The graph is a straight line through the origin. Its slope represents

21. The electric field lines of a positive isolated point charge are best described as

22. A source charge produces electric field at distance . If the source charge becomes and the medium is changed to a dielectric of constant , with the same distance , the new field magnitude is

23. Use the arrangement described below: two forces of equal magnitude act on a small charged body, one toward east and the other toward west. The net force on the body is

24. In deriving the field of an infinite line charge using a cylindrical Gaussian surface, the flux through the two flat end caps is zero because

25. For a far axial point of a dipole, where , the approximate field magnitude is

26. The approximate value of Coulomb’s constant in vacuum is

27. A spherical shell of radius carries charge . The electric field magnitude at a point from the centre is

28. Study the table for electric field directions at point on the -axis. Identify the row that needs correction.

29. For a dipole in a uniform electric field, the potential energy is minimum when the angle between and is

30. A listed charge value for an isolated particle-like body is . With , this value is not allowed as a net charge because

31. Electric charge is additive. This means that the total charge of a system is found by

32. The sign acquired by a body during rubbing depends mainly on

33. In the vector form of Coulomb’s law, the unit vector is needed mainly to show

34. If were larger while all other charge and distance values were unchanged in vacuum-form Coulomb’s law, the value of would

35. A table describes force directions for two charges on a horizontal line. Identify the row that is inconsistent.

36. A student says, “A charge placed in an electric field must move exactly along an electric field line.” The statement is incomplete because

37. A square has side . A charge is placed at one corner, and a charge is placed at the diagonally opposite corner. The separation between the charges is

38. Electric field lines are drawn closer together in one region and farther apart in another. The closer spacing indicates that the electric field in that region is

39. A claim says, “When two neutral bodies are rubbed, one becomes charged because charge is created on it, while the other remains truly unchanged.” The best evaluation is that the claim

40. A charge placed at a point experiences a force of magnitude . The electric field magnitude at the point is

41. A charge is at . Two charges on the same line exert forces on it: toward left and toward right. Taking right as positive, the vector net force is

42. A charged conductor touches a neutral conductor. The final charge acquired by the neutral conductor depends on the

43. A pillbox Gaussian surface of flat-face area crosses an infinite plane sheet of surface charge density . The enclosed charge is

44. Charges , , and are fixed on a straight line in that order, with equal spacing. The net force on the middle charge is zero because

45. Study the dipole statements below.
I. An electric dipole has zero net charge.
II. The dipole moment magnitude is charge magnitude multiplied by separation.
III. The dipole moment vector points from to .
IV. A dipole can have non-zero dipole moment even though its net charge is zero.
The supported statements are

46. The property that best separates conductors from insulators in electrostatics is

47. A graph of versus for a uniformly charged thin spherical shell of radius is compared with a graph for an infinite line charge. The correct comparison is

48. The permittivity of a medium with dielectric constant is related to the vacuum permittivity by

49. A neutral glass rod is rubbed with silk and becomes positively charged. If the rod has charge , the number of electrons lost by the rod is approximately .

50. A point charge produces electric field at distance . At the same time, an infinite line charge produces field at distance . If the distance from both sources is increased to , the ratio of the point-charge field to the line-charge field becomes