25 MCQs | Physics | Class XII | Electrostatic Potential and Capacitance

 

TEST OF ELECTROSTATIC POTENTIAL AND CAPACITANCE

1.    For a positive charge q, Select the option which correctly represents the graph of Electrostatic Potential V and Electrostatic field E with distance from that charge r . Take E,V on y axis and r on X axis.


a)      Graph 1, ____- E, _ _ _ _ - V

b)     Graph 2, ____- V, _ _ _ _ - E

c)      Graph 1, ____- V, _ _ _ _ - E

d)     Graph 2, ____- E, _ _ _ _ - V


Answer

Answer : c

2.    If the potential of a hollow metallic sphere on its surface is 106 Volt, what is the potential at any point inside the sphere?

a)      Less than 106 Volt

b)     More than 106 Volt

c)      Equal to 106 Volt

d)     Insufficient data in question.

 

Answer

Answer : c

3.    Which formula correctly denotes the Electric field due to infinite plane sheet of charge of surface charge density α.

a)      α/2εo

b)     2α/εo

c)      α/εo

d)     εo/ α

 

Answer

Answer : a

4.    Which of the following properties is not correct with regard to equipotential surfaces?

a)      In the regions of stronger Electric field, the equipotential surfaces are closer.

b)     No two equipotential surfaces can intersect each other.

c)      Electric field is always normal to equipotential surface at every point.

d)     Equipotential surface is spherical for a uniform Electric Field.

 

Answer

Answer : d

5.    What is the nature of equipotential surface due to a point charge placed at infinity?

a)      Plane

b)     Spherical

c)      Elliptical

d)     Cylindrical

 

Answer

Answer : a

6.    The dimensions of fall of potential per unit distance are given by:

a)      [MLT-3 A-1]

b)     [ML2T-2A-1]

c)      [ML2T-2A-3]

d)     [MLT-2A-2]

 

Answer

Answer : a

7.    Three capacitors of capacitances 3µF, 9µF and 18 µF are connected once in series and then in parallel. The ratio of equivalent capacitances Cs/Cp will be

a)      1:15

b)     1:1

c)      15:1

d)     1:3

 

Answer

Answer : a

8.    Two capacitors of capacitance 6 µF and 4 µF are put in series across a 120 V battery. What is the potential difference across the 4 µF capacitor ?

a)      72 V

b)     60 V

c)      48 V

d)     Zero

 

Answer

Answer : a

9.    Two insulated charged spheres of radii 20 cm and 25 cm respectively and having an equal charge q are connected by a copper wire and then they are separated.

a)       Both spheres will have the same charge q.

b)     Charge on sphere of radius 20 cm will be more than that of radius 25 cm.

c)      Charge on sphere of radius 20 cm will be lesser than that of 25 cm.

d)     Charge on each will be Zq.

 

Answer

Answer : c

10. The electric potential of earth is taken as:

a)     Zero

b)     Infinity

c)     Unity

d)     None of these

 

Answer

Answer : a

11. Five equivalent capacitors each with capacitance C are connected as shown in figure. The equivalent capacitance across A and B is :

 



a)      5 C

b)     C

c)      C/5

d)     3C

 

Answer

Answer : b

12.  In a parallel plate capacitor, the capacity increases if

a)     Area of plate is decreased

b)     Distance between plates increases

c)     Area of plate is increased

d)     Dielectric constant decreases

 

Answer

Answer : c

13. Assertion: For a system of positive test charge and point charge, Electric Potential Energy=Electric Potential

Reason: Electric Potential and Electric Potential Energy are different quantities

a)      Both Correct, R is correct explanation of A

b)     Both Correct, R is incorrect explanation of A

c)      A correct, R incorrect

d)     A incorrect, R correct

 

Answer

Answer : d

14. Charge of 12 µC is given to a hollow metallic sphere of radius 0.1 m. Find the potential at (i) surface of the sphere, (ii) centre of the sphere.

a)      (i) 1.08 X 106V, (ii) 0 V

b)     (i) 1.08 X 106V, (ii) 1.08 X 106V

c)      (i) 1.08 X 107V, (ii) 0 V

d)     (i) 1.08 X 107V, (ii) 1.08 X 107V

 

Answer

Answer : b

15. Two positive point charges of 0.02 µC and 0.01 µC are placed 10 cm apart. Calculate work done in reducing them to a distance of 5 cm.

a)      1.8 X 10-5 J

b)     1.8 X10-6 J

c)      0.9 X 10-4 J

d)     9 X10-6 J

 

Answer

Answer : a

16.  If the capacitance of a conductor carrying a charge of 8 C is 0.005 F, calculate its potential.

a)      0.04 V

b)     0.000625 V

c)      1600 V

d)     0.32 V

 

Answer

Answer : c

17. A positive charge initially at rest is allowed to freely move in an Electric field. What will happen to its potential energy ?

a)      Remains constant because Electric field is uniform.

b)     Increase because charge moves along Electric field

c)      Decreases because charge moves along Electric Field

d)     Decreases because charge moves opposite to Electric Field

 

Answer

Answer : c

18.  The electric potential at any equatorial point of an electric dipole is :

a)      Directly proportional to distance

b)     Inversely proportional to distance

c)      Zero

d)     Inversely proportional to square of the distance.

 

Answer

Answer : c

19. There are two metallic spheres of same size, one hollow and the other solid. Which of the following statements is True ?

a)      Solid sphere can be charged more due to more electrons present in it.

b)     Hollow sphere can be charged more.

c)      Both can be charged equally

d)      None of the above

 

Answer

Answer : c

20. An equipotential surface is that surface in which

a)      Surface has zero potential

b)     Surface has same potential at all the points

c)      Surface has negative potential than points outside

d)     Surface has positive potential  than point outside.

 

Answer

Answer : b

21.  Energy stored in a capacitor is given by :

a)      ½ VC2

b)     ½ V2C2

c)      ½ V2C

d)     ½ VC

 

Answer

Answer : c

22.  1 eV is equivalent to :

a)      1.6 X 10-19 J

b)     1.6 X 10-19 V

c)      1.6 X 10-19 C

d)     None of the above

 

Answer

Answer : a

23. Which of the following statements are True about the potential difference ?

(i)        It depends only on the initial and final position and not on the oath followed.

(ii)      It is the work done in moving the charge form one point to other.

(iii)     It is more if we calculate it for 2 C than if we calculate it for 1 C.

a)   I only

b)   II only

c)    I and II only

d)   I, II and III

 

Answer

Answer : c

24. A conductor contains some charge. It is connected to another uncharged conductor with a wire. Now, the energy of the new system so formed is :

a)      More than the first case

b)     Less than the first case

c)      Remains same as the first scenario

d)     None of the above

 

Answer

Answer : b

25. The capacitance of earth, viewed as a spherical conductor of radius 6408 km is:

a)     1420 µF

b)     712 µF

c)     680 µF

d)     540 µF

 

Answer

Answer : b

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