# Class 12 Physics : Electrostatics Revision Test

Max marks:50 Time:2hrs

1. A glass rod rubbed with silk acquires a charge of 6×10-12 C. Calculate the number of electrons it has gained or lost. (1)
2. If the magnitude of each charge becomes doubled, the separation between them is halved and the system of charges kept in a medium of=3 Calculate the force between them. (1)
3. If two equal charges separated by a distance of 2m in air medium experiences a force of 0.9×1010 C, Calculate the magnitude of each charge. (1)
4. Electric field intensity is 400Vm-1 at a distance of 2 m from a point charge. At what distance it will become 100 Vm-1? (1)
5. What will be the force experienced by a particle of charge 2µC placed in an electric field of 10kVm-1? (1)
6. What is the work done by moving 400μF charge between two points separated by a distance of 27 cm on an equipotential surface? (1)
7. Calculate the number of electric lines of force from a charge 1.7708X10-6 C in air medium? (1)
8. Two protons ‘A’ and ‘B’ are placed between two parallel plates having a potential difference ‘V’ as shown in the figure. Will these protons experience equal or unequal force? (1)
9. Draw an equipotential surface for a point charge q> 0(1)
10. The capacitance of a parallel plate capacitor is ‘C’. If 15 such capacitors are connected in series and then in parallel, what is the ratio of effective capacitance of first case to the second? (1)
11. What is electric polarization ,polar and non polar molecules?( 2)
12. 2) Define electrostatic induction and corona discharge. ( 2)
13. Calculate the ratio of force experienced by a proton to that of the electron placed in an electric field of 4KVm-1. ( 2)
14. If an electrician has three capacitors of capacitances 4µF, 7µF& 12µF. How should he connect them, So that the effective capacitance will be 10µF? ( 2)
15. Define the SI unit of potential difference and charge. ( 2)
16. Two charges of 20µC and -20µC are placed 20 cm apart at points A and B respectively. Compute the electric field strength at point C, 20 cm away from both A and B.(3)
17. Three capacitors of capacitances 4µF, 6µF and 8µF are connected parallel to each other and the combination is connected across a battery of 25V. Calculate the charges present on each capacitor and the total charge flows from the source. (3)
18. Derive an expression for the torque experienced by a dipole in an external electric field. (3)
19. Obtain an expression for the capacitance of a parallel plate capacitor. (3)
20. Derive the relation E= (3)
21. Derive an expression for the potential at a point due to dipole. Write the special cases also.(5)
22. Derive an expression for ‘E’ at a point on the axial line of the dipole. (5)
23. Explain with a neat diagram the principle, construction and working of a Van de Graff generator. (5)

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