Electric Charges and Fields Mock Test – Class 12 Physics

1. A body has charge . The negative sign mainly tells that the charge

2. Two identical isolated conducting spheres initially carry and . After touching and separating, one of them is touched to a third identical neutral sphere and then separated. The final charge on the first sphere after the second contact is

3. The principle of superposition for electrostatic force says that the net force on a charge due to several other charges is found by

4. A charge is placed between a negative charge on its left and a positive charge on its right. The force on due to both outer charges is

5. Read the situation below and answer the question.

What can be inferred about block P after rubbing?

6. A charged spherical conductor and a uniformly charged thin spherical shell have the same radius and total charge . For points outside them, their electric fields are

7. For an infinite uniformly charged plane sheet with surface charge density , the electric field is directed

8. Assertion: Coulomb force and gravitational force both obey superposition.
Reason: In each case, the net force due to several sources is found by vector addition of individual force contributions.

9. Charge is at the origin and charge is on the positive -axis. With , the sign of in makes the force on

10. A charge is uniformly spread on a thin spherical shell of radius . If the shell radius is doubled while the total charge stays , the electric field at a fixed outside point from the centre, with still larger than the new radius, is

11. The density expression that would be most suitable for a long thin charged thread is

12. Two equal positive point charges are fixed at equal distances on the left and right of point . The electric field at due to these two charges is

13. A compound setup has a point charge at distance , an infinite line charge with density at distance , and an infinite plane sheet with density . Their field magnitudes at the same point are equal. The relation among , , , and is

14. Three charges lie on the -axis. A charge at the origin experiences toward due to a charge on the left and toward due to a charge on the right. The net force on is

15. A conducting sphere is charged and isolated. At a point just outside the surface, the electric field is . If the local surface charge density at that point is doubled by redistribution, the field just outside that point becomes

16. A diagram for two equal unlike charges shows many lines going from the positive charge to the negative charge. At the midpoint between the charges, the electric field is directed

17. A unit vector is defined from charge toward charge . For the force on due to , a suitable vector form is

18. A graph has three labelled curves for electric field magnitude against distance . Curve P falls as , curve Q falls as , and curve R is horizontal. The most suitable source matching is

19. A positive charge and another positive charge are fixed on a straight line. The point where the net electric field is zero lies

20. A negatively charged rod is brought near, but does not touch, a neutral metal sphere on an insulating stand. The near side of the sphere becomes relatively positive. This happens because

21. A thin wire is made of two equal halves. The left half carries , and the right half carries . The distribution along the wire is best described as

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

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

24. A uniformly charged infinite line has linear charge density . The electric field at distance from the line is directed

25. A small sphere marked is brought near another small sphere marked . The interaction between them is expected to be

26. A closed surface has total outward electric flux . The negative sign means that, overall,

27. Study the comparison table for a far electric dipole field and identify the mismatched row.

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

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

30. A point charge produces field at distance in vacuum. The source charge is doubled, the distance is tripled, and the space is filled with a dielectric of constant . The new field magnitude is

31. A charge is placed at the centre of a cube. The flux through one face is . The charge is

32. A Coulomb-law calculation uses , , , and . The force magnitude is

33. A far dipole field is compared with the field of a single point charge. The dipole field decreases faster with distance because it varies as

34. A uniformly charged spherical shell and an infinite line charge give equal electric fields at , where is measured from the shell centre and from the line respectively. At , the ratio is

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

36. Two charges are changed from and to and , with separation unchanged. The new force magnitude is

37. 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

38. The potential energy of an electric dipole in a uniform electric field is

39. A closed cubical surface is placed in a uniform electric field, with the field entering one face and leaving the opposite face. If no charge is enclosed, the net electric flux through the cube is

40. Match each charge density with its defining expression.

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

42. Study the table about force and field directions. Identify the row that needs correction.

43. A student writes . This value represents

44. The unit of can be inferred from . If is in , charge is in , and distance is in , the unit of is

45. Two large parallel sheets carry and . A proton is released from rest between them. Its initial acceleration is

46. Assertion: The electric field inside the material of a conductor in electrostatic equilibrium is zero.
Reason: If a non-zero electric field existed inside the conductor, free charges would experience force and move.

47. A graph of versus for an infinite line charge of fixed is a straight line through the origin. The slope represents

48. The SI unit of electric flux is

49. Two charges produce forces on a third charge along the same straight line. One contribution is and the other is , where means toward the right. The net force is

50. Consider the following statements about a dipole in an external electric field.
I. In a uniform electric field, the net force on the dipole is zero.
II. In a non-uniform electric field, the dipole may experience a net force.
III. A dipole in a non-uniform field can still experience torque.
IV. A non-uniform field changes the two charges of a dipole into equal positive charges.
The supported statements are