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# Physics XII (S-II)

I Revise the complete unit Electrostatics

1. What is electrostatic potential due to an electric dipole at an equatorial point?

2. Draw three equipotential surfaces corresponding to i) a uniform electric field ii) an electric dipole

3. Define electric flux. Write its SI unit. A charge ‘q’ is enclosed by a spherical surface of radius R. If the radius is reduced to half, how would the electric flux would change?

4. A parallel plate capacitor is charged by a battery. After some time the battery is disconnected and a dielectric slab of dielectric constant K is inserted between the plates. How would i)the capacitance ii) the electric field between the plates and iii) the energy stored in the capacitor be affected? Justify your answer.

5. A charge +Q is placed on a large spherical conducting shell of radius ‘R’. Another small conducting sphere of radius ’r’ is introduced in the large shell and is placed at its centre (a) Find the potential difference between two pints, one lying on the sphere and the other on the shell (b)How would the charge between the two flow if they are connected by a conducting wire? Name the device which work on this fact.

6. The sum of two point charges is 7µC.They repel each other with a force of 1N when kept 30cm apart in free space.Calculate the value of each charge.

7. Define the term electric dipole moment .Is it a scalar or vector?

Deduce an expression for the electric field at a point on the equatorial plane of an electric dipole of length’ 2a’

Ms T.L.Bindu, PGT (Phy)