Chapter-01 Electric Charges and Fields Test Paper-2

Class - 12 Physics (Electric Charges and Fields)

1. A charge q is placed at the center of the line joining two equal charges Q. The system of the three charges will be in equilibrium if q is equal to

2. A half ring of radius R has a charge of per unit length. The field at the center is

3. A point charge +10 is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Figure. What is the magnitude of the electric flux through the square?

4. When a negatively charged conductor is connected to earth

a. Electrons flow from the earth to the conductor
b. Protons flow from the conductor to the earth
c. No charge flow occurs
d. Electrons flow from the conductor to the earth

5. Eight dipoles of charges of magnitude e are placed inside a cube. The total electric flux coming out of the cube will be

6. Define dipole moment of an electric dipole. Is it a scalar quantity or a vector quantity?

7. A proton is placed in a uniform electric field directed along the positive X-axis. In which direction, will it tend to move?

8. A charge q is placed at the centre of a cube of side I. What is the electric flux passing through each face of the cube?

9. Sketch lines of force due to two equal positive charges placed at a small distance apart in air.

10. Plot a graph showing the variation of Coulomb force (F) versus 1/
r2, where r is the distance between the two charges of each pair of charges (1µC, 2µC) and (1µC, -3µC). Interpret the graphs obtained.

11. An electric dipole of length 4 cm when placed with its axis making an angle of 60° with a uniform electric field, experiences a torque of 4√3 N-m. Calculate the potential energy of the dipole if it has charge of ± 8nC.

12. i. Obtain the expression for the torque experienced by an electric dipole of dipole moment p in a uniform electric field, E.
ii. What will happen, if the field were not uniform?

13. Suppose that the particle in an electron projected with velocity
vx = 2.0 × 106 ms-1. If E between the plates separated by 0.5 cm is 9.1 × 102 N/C, where will the electron strike the upper plate?

14. Two concentric metallic spherical shells of radii R and 2R are given charge Q1 and Q2 respectively. The surface charge densities on the outer surfaces of the shells are equal. Determine the ratio Q1 : Q2.

15. Find the magnitude of the resultant force on a charge of 1μC held at P due to two charges of
+2 × 10-8 C and -10-8 at A and B respectively. Given AP = 10 cm and BP = 5 cm , ∠APB = 90°.

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