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# Physics XII (S-II)

Ms T. L. Bindu, PGT (Phy)

Date of submission: 23 June 2014

1. Two insulated charged copper spheres A and B of identical size have charges qA and qB respectively. A third sphere C of the same size but uncharged is brought in contact with the first, then brought in contact with the second and finally removed from both. What are the new charges on A and B?

2. What does q1+q2=0 signify in electrostatics.

3. If the distance between two equal point charges is doubled and their individual charges are also doubled, what would happen to the force between them?

4. Force between two point charges kept at a distance d apart in air is F.If these charges are kept at the same distance in water, how does the electric force between them change?

5. Name the physical quantity whose SI unit is1) N/C 2)J/C ?

6. In an electric field an electron is kept freely. If the electron is replaced by a proton, what will be the relationship between the forces experienced by them?

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. An electric dipole is placed in a uniform electric field. What is the net force acting on it?

9. A dipole of dipole moment p is present in a uniform electric field E .Write the value of angle between p and E for which the torque experienced by the dipole is minimum.

10. If the radius of the Gaussian surface enclosing the charge is halved, How does the electric flux through the Gaussian surface change?

11. 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,2 µC) and(2 µC ,-3µC).Interpret the graphs obtained.

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

13. A hollow metal sphere of radius 5cm is charged such that its potential on its surface is10V.What is the potential at the centre of the sphere?

14. Write down the relation between electric field and electric potential at a point.

15. In which orientation ,a dipole placed in a uniform electric field is in i) stable equilibrium ii) unstable equilibrium

16. Draw an equi potential surface for a system, consisting of two charges +Q, -Q separated by a distance r in air.

17. 5J of work is done in moving a positive charge of 0.5 C between two points. What is the potential difference between these two points?