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#### Electrostatics Model Question Paper

12th Standard EM

Reg.No. :
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Physics

Time : 02:00:00 Hrs
Total Marks : 60
8 x 1 = 8
1. Which charge configuration produces a uniform electric field?

(a)

point Charge

(b)

infinite uniform line charge

(c)

uniformly charged infinite plane

(d)

uniformly charged spherical shell

2. An electric dipole is placed at an alignment angle of 300 with an electric fi eld of 2 × 105 NC-1. It experiences a torque equal to 8 N m. Th e charge on the dipole if the dipole length is 1 cm is

(a)

4 mC

(b)

8 mC

(c)

5 mC

(d)

7 mC

3. An electric field $\vec { E } =10x\hat { i }$ exists in a certain region of space. Then the potential difference V = Vo – VA, where Vo is the potential at the origin and VA is the potential at x = 2 m is:

(a)

10 J

(b)

-20 J

(c)

+20 J

(d)

-10 J

4. Two metallic spheres of radii 1 cm and 3 cm are given charges of -1 x 10-2 C and 5 x 10-2 C respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is

(a)

3 × 10-2 C

(b)

4 × 10-2 C

(c)

1 × 10-2 C

(d)

2 × 10-2 C

5. The electrostatic force obeys _______.

(a)

Newton's I law

(b)

Newton's II law

(c)

Newton's III law

(d)

none of the above

6. The electrostatic force is always greater in magnitude than gravitational force for_________ object.

(a)

bigger size

(b)

smaller size

(c)

medium size

(d)

all the above

7. The relative permittivity of water is _______.

(a)

εr= 70

(b)

εr=75

(c)

εr=80

(d)

εr=85

8. Eight mercury droplets having a radius of 1 mm and charge of 0.066 pC each merge to form one droplet. Its potential is

(a)

2.4 V

(b)

1.2 V

(c)

3.6 V

(d)

4.8 V

9. 5 x 1 = 5
10. Benjamin Franklin

11. (1)

εr= 1

12. Thales

13. (2)

Vector quantity

14. Air

15. (3)

Frictional electricity

16. permittivity of free space

17. (4)

Lightning Arrestor

18. Electric field

19. (5)

8.854 x 10-12 C2N-1m-2

2 x 2 = 4
20. (a) Mica
(b) Ebonite
(c) Aluminium
(d) Oil

21. (a) ∝ - particle
(b) electron
(c) proton
(d) deutron

22. 2 x 1 = 2
23.  a) NH3 - Non - polar molecule b) O2 - Polat molecule c) Mica - Conductor d) Ceramic - Capacitor
24.  a) Volt - electric current b) C/m - electric dipole moment c) NC-1 - electric field intensity d) C2Nm2 - electric flux
25. 8 x 2 = 16
26. What is meant by quantisation of charges?

27. What are the differences between Coulomb force and gravitational force?

28. Define ‘Electric field’.

29. Define ‘Electric dipole’.

30. Define ‘electric flux’.

31. What is Polarisation?

32. What is corona discharge?

33. What are Polar molecules.

34. 5 x 3 = 15
35. Consider two point charges q1 and q2 at rest as shown in the figure.

They are separated by a distance of 1m. Calculate the force experienced by the two charges for the following cases:
(a) q1 = +2μC and q2 = +3μC
(b) q1 = +2μC and q2 = -3μC
(c) q1= +2μC and q2 = -3μC kept in water (εr = 80)

36. Discuss the basic properties of electric charges.

37. Define ‘Electric field’ and discuss its various aspects.

38. Derive an expression for electrostatic potential due to a point charge.

39. Explain in detail how charges are distributed in a conductor, and the principle behind the lightning conductor.

40. 2 x 5 = 10
41. A water molecule has an electric dipole moment of 6.3 × 10-30 Cm. A sample contains 1022 water molecules, with all the dipole moments aligned parallel to the external electric field of magnitude 3 × 105 NC-1. How much work is required to rotate all the water molecules from θ = 00 to 900?

42. Dielectric strength of air is 3 × 106 V m-1. Suppose the radius of a hollow sphere in the Van de Graff generator is R = 0.5 m, calculate the maximum potential difference created by this Van de Graaff generator.