#### Electrostatics One Marks Question with Answer

12th Standard EM

Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 25
25 x 1 = 25
1. An isolated metal sphere of radius 'r' is given a charge' q'. The potential energy of the sphere is

(a)

$\frac { { q }^{ 2 } }{ 4\pi { \varepsilon }_{ 0 }r }$

(b)

$\frac { { q }^{ } }{ 4\pi { \varepsilon }_{ 0 }r }$

(c)

$\frac { { q }^{ } }{ 8\pi { \varepsilon }_{ 0 }r }$

(d)

$\frac { { q }^{ 2 } }{ 8\pi { \varepsilon }_{ 0 }r }$

2. Charge per unit volume is called

(a)

Linear charge density (λ)

(b)

Surface charge density (σ)

(c)

Volume charge density (ρ)

(d)

Electric flux

3. The expression for the electric field due to a surface of total charge 'Q' is given by

(a)

$\overset { \rightarrow }{ E } =\frac { 1 }{ 4\pi { \varepsilon }_{ 0 } } \int { \frac { \sigma dA }{ { r }^{ 2 } } } \hat { r }$

(b)

$\overset { \rightarrow }{ E } =\frac { 1 }{ 4\pi { \varepsilon }_{ 0 } } \int { \frac { \rho dA }{ { r }^{ 2 } } } \hat { r }$

(c)

$\overset { \rightarrow }{ E } =\frac { 1 }{ 4\pi { \varepsilon }_{ 0 } } \int { \frac { \lambda dl }{ { r }^{ 2 } } } \hat { r }$

(d)

$\overset { \rightarrow }{ E } =\frac { 1 }{ 4\pi { \varepsilon }_{ 0 } } \int { \frac { dq }{ { r }^{ 2 } } } \hat { r }$

4. The electric flux is negative, if the angle between $\overset { \rightarrow }{ dA }$ and $\overset { \rightarrow }{ E }$ is

(a)

Less than 90°

(b)

greater than 90°

(c)

equal to 90°

(d)

equal to 0°

5. In the given cricuit the effective capacitance between A and B will be

(a)

3μf

(b)

$\frac{36}{13}$ μf

(c)

13μf

(d)

7μf

6. The direction of electric field at a point the equatorial line due to an electric dipole is

(a)

along the equatorial line towards the dipole.

(b)

along the equatorial line away from the dipole

(c)

parallel to the axis of the dipole and opposite to the direction of dipole moment

(d)

parallel to the axis of the dipole and in the direction of dipole moment.

7. The lower comb of van de graaff generator is maintained at a positive potential of

(a)

10 kV

(b)

107 V

(c)

100 V

(d)

103 V

8. Two charges are kept at a distance in air what should be the relative permittivity of the medium in which the two charges should be kept at the same distance so that they experience half of the force which they experienced in air?

(a)

$\frac{1}{2}$

(b)

$\frac{1}{0.2}$

(c)

2

(d)

0.2

9. In tuning radio we use,

(a)

capacitors

(b)

transistors

(c)

diodes

(d)

LEDS

10. The capacitance of a parallel plate capacitor increases from 5μf of 50μf when a dielectric is filled between the plates. The permitivity of the dielectric is

(a)

8.854x10-12C2N-1 m-2

(b)

8.854x10-11C2N-1 m-2

(c)

10x10-12C2N-1 m-2

(d)

12x10-12C2N-1 m-2

11. Region around a charge q in which it exerts force on a test charge is called

(a)

electric flux intensity

(b)

electric force

(c)

electric field

(d)

Coulomb's force

12. Which of the following cannot be the units of electric field intensity?

(a)

NC-1

(b)

Vm-1

(c)

JC-1/m

(d)

JC-1

13. The electric flux through a surface will be minimum when the angle between Eand A is

(a)

90°

(b)

60°

(c)

(d)

45°

14. A charge Q is placed at the corner of a cube. The electric flux through all the six faces of the cube is

(a)

$\frac { Q }{ { 3\varepsilon }_{ 0 } }$

(b)

$\frac { Q }{ { 6\varepsilon }_{ 0 } }$

(c)

$\frac { Q }{ { 8\varepsilon }_{ 0 } }$

(d)

$\frac { Q }{ { \varepsilon }_{ 0 } }$

15. What physical quantities may X and Y represent? [Y represents the first mentioned quantity].

(a)

K.E - velocity of a particle

(b)

pressure - temperature of a given gas (constant volume)

(c)

capacitance - charge to give a constant potential

(d)

potential - capacitance to give a constant charge

16. During charging a capacitor variation of potential V of the capacitor with time t as shown a

(a)

(b)

(c)

(d)

17. A condenser of 2μF capacitance is charged steadily from 0 to 5 coulomb. Which of the following graphs correctly represents the variation of potential difference across its plates with respect to the charge on the condensor [Q = C V ]

(a)

(b)

(c)

(d)

18. A charge q is enclosed as shown in fig. The electric flux is

(a)

maximum in (i)

(b)

maximum in (ii)

(c)

maximum in (iii)

(d)

equal in all

19. A charge q1 exerts force on charge q2. If another charge q3 is brought near, the force of q1, exerted on q2, will be

(a)

decreased

(b)

increased

(c)

remains unchanged

(d)

increased if q3 is of same sign as q1 and decreased if q2 is of opposite sign.

20. Which instrument was used to demonstrate the electrostatic shielding?

(a)

Lightning arrester

(b)

Van de graaff generator

(c)

(d)

Gold leaf electroscope

21. When a point charge of 6mC is moved between two points in an electric field, the work done is 1.8 x 10-5 J. The potential difference between the two points is

(a)

1.08 V

(b)

1.08 μV

(c)

2 V

(d)

30 V

22. A closed system contains four charges -8.1C, 14.6C, 20.2C and -200 mC. The total charge in the system_______.

(a)

26.5 C

(b)

-173.3 C

(c)

43.1 C

(d)

243.9 C

23. The unit of electric field intensity is _______.

(a)

NC-1

(b)

NC-1C2m-1

(c)

Cm

(d)

Volt-meter

24. Two point charges +q and -q are placed at points A and B respectively separated by a small distance. The electric field intensity at the midpoint O of AB :

(a)

is zero

(b)

acts along AB

(c)

acts along BA

(d)

acts perpendicular to AB

25. When an electric dipole of dipole moment p is aligned parallel to the electric field E then the potential energy of the dipole is given as _________.

(a)

pE

(b)

zero

(c)

-pE

(d)

$\frac{pE}{\sqrt{2}}$