## Tuesday, July 26, 2011

### Electrostatic Potential and capacitance Physics Revision Test for Class XII

Electrostatic Potential and Capacitance

`Max. Marks :: 30                                      Time:: 75 minutes`

1 mark questions

1. Define electric potential.

3. State the principle of a capacitor.

4. Draw the equipotential surface for a point charge q>0.

5. Define dielectric constant of a medium on the basis of capacitance.

6. Write the ratio of electric potential at a distance r on equatorial position to the electric potential at a distance r on axial position.

7. Calculate the radius of a spherical conductor of capacitance 1 pF.

8. What is electrostatic shielding?2 Marks Questions

9. A regular hexagon of side 10 cm has a charge 5 μC at each of its vertices. Calculate the potential at the centre of the hexagon.

10. Derive an expression for the energy stored in a capacitor.

11. Four capacitors are connected as shown in diagram. Calculate the equivalent capacitance between the points X and Y. 12. When two capacitors of capacitance C1 and C2 are connected in series, the net capacitance is 3μF . When connected in parallel the effective capacitance is 16μF. Calculate the values of C1 and C23 marks questions

13. Derive an expression for the capacitance of a parallel plate capacitor with a dielectric slab of thickness less than the spacing between the the plates inserted between the plates.

14. A 10μF capacitor is charged by a 30V dc supply and then connected across a an uncharged 50μF capacitor. Calculate (i) the final potential difference across the combination, and (ii) the initial and final energies. How will you account for the difference in energy?

15. A parallel plate capacitor with air between the plates has a capacitance of 8 pF. What will be the capacitance if the distance between the plates is reduced by half and the space betwee them is filled with a substance of dielectric constant K = 6?5 Marks Questions

16. Describe the principle construction and working of a Van de Graff generator. Explain why the apparatus is enclosed inside a steel chamber maintained at high pressure.