Electric Charges and Fields Mock Test – Class 12 Physics

1. A charge is placed at the centre of a square. Four identical positive charges are fixed at the four corners. If the centre charge is removed, the electric field at the centre due to the four corner charges is

2. A plane surface of area is placed in a uniform electric field . Select the row with the correct flux sign when is the angle between and .

3. A positively charged rod is brought near a neutral conducting sphere. The sphere is connected to earth and then isolated while the rod is still present. After the rod is removed, the charge spreads over the sphere because

4. The convenient Gaussian surface for an infinitely long uniformly charged straight wire is a cylinder coaxial with the wire because

5. A flat surface is placed in a uniform electric field so that the electric field is parallel to the surface. The electric flux through the surface is

6. Two equal-magnitude electrostatic forces act on a charge at right angles to each other. The magnitude of the resultant force is

7. A point charge is placed at , and a point charge is placed at . The magnitude of the electric field at the origin due to the charge is . The electric field vector at the origin due to is

8. Coulomb’s law in scalar magnitude form gives the electrostatic force between two

9. An electric field graph for a source is given by . If the graph of against has slope , and , the source and observation line are best identified as

10. The dimensional formula of can be obtained from . Taking charge dimension as , the dimension of is

11. In electrostatics, the symbols and should not be confused because

12. Two charges and are fixed apart. A small positive test charge is placed between them at a point where the net electric field is zero. Its distance from is

13. An infinite line charge has density . A coaxial cylindrical Gaussian surface of radius and length is used. If both and are doubled, the electric field on the curved surface becomes

14. A charge is placed exactly midway between two identical charges fixed on its left and right at equal distances. The net force on the middle charge is

15. A dipole has moment . At a far axial point from its centre, the approximate field magnitude in vacuum is

16. Two small charged bodies have charges and . They are treated as one composite system. The system is

17. A charged conducting sphere of radius has surface charge density . The electric field just outside its surface is compared with the electric field at distance from its centre. The ratio is

18. A dipole has moment . At a far axial point, a student writes because Coulomb’s law has an inverse-square form. The correction is that the far dipole field varies as

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

20. A point charge produces an electric field at a point away in vacuum. Take . The field magnitude is

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

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

23. The scalar magnitude form of Coulomb’s law in vacuum is

24. A neutral conducting sphere is charged by induction using a positively charged rod. The rod never touches the sphere. After the proper earthing sequence, the sphere becomes

25. Study the closed-surface flux statements and identify the row that needs correction.

26. Two fixed point charges are kept at the same separation, but the experiment is repeated in a medium of dielectric constant . In a graph of versus , the slope in the medium becomes

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

28. Study the derivation steps for a point charge using a spherical Gaussian surface and identify the row that needs correction.

29. If the far axial field of a dipole is at distance , then at distance on the same axial line it becomes

30. The electric field of an ideal infinite uniformly charged plane sheet is independent of distance from the sheet because

31. An electron enters a uniform electric field of magnitude with initial velocity perpendicular to the field. If its initial speed is and the field region has length along the initial velocity direction, the vertical deflection magnitude on leaving the region is

32. A non-uniformly charged rod is divided mentally into very small pieces. The use of in is helpful because

33. A point charge produces electric field at distance . If the distance is doubled while the source charge and medium remain unchanged, the field becomes

34. A closed isolated system initially has net charge . After internal charge transfer among its parts, the final net charge must be

35. 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

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

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

38. The relation says that when the separation is doubled while the charges stay the same, the force becomes

39. Two charges and are fixed on a line. At a point between them, a positive test charge experiences

40. A comparison of common Gauss-law field results is shown below.

Which source has electric field magnitude independent of distance?

41. A spherical Gaussian surface encloses a point charge at its centre. If the radius of the sphere is doubled, the total electric flux through the sphere becomes

42. Two points are at distances and from the same infinitely long uniformly charged wire. If the electric field at distance is , the electric field at distance is

43. A uniformly charged spherical shell of radius has charge . An infinite line charge has density . Their fields are equal at a point where from the shell centre and from the line. The relation between and is

44. Study the table for two isolated conducting spheres after they touch and separate.

The row that does not follow equal sharing for identical spheres is

45. In charging by friction, the two rubbed bodies usually acquire equal and opposite charges because

46. The statement represents the quantisation of electric charge, where must be

47. A dipole has at and at . At a point on the positive -axis with , where , the net electric field due to the dipole is directed

48. A positive test charge is placed outside two equal positive charges, to the right of both charges. The force contributions on the test charge due to the two fixed charges are

49. A field-line diagram around two charges shows lines starting on charge P and ending on charge Q. The most suitable identification is

50. A formula sheet shows the two expressions and in the same electrostatics section. Their usual connection in vacuum electrostatics is