Tuesday, July 26, 2011

Physics Revision Test for Class XII :: Electric Charges and Field


Max. Marks: 30                 Time: 75 minutes

(Please take care to complete the test in the prescribed time limit)

One mark Questions

  1. Define electric flux.

  2. How is the force between two charges affected when dielectric constant of the medium in which they are placed increases?

  3. Name the physical quantity whose SI unit is NC-1

  4. Why two electric lines of force never intersect each other?

  5. Define dielectric constant of a medium.

  6. What is an ideal dipole?

  7. Write the SI unit of electric dipole moment.

  8. Calculate the number of electrons making a charge of -0.1 mC.
    2 Marks questions

  9. Vehicles carrying inflammable materials have metallic ropes (or chains)touching the ground while in motion. Explain why is it necessary?

  10. Derive an expression for the electric field intensity at a distance 'r' from a point charge 'q'

  11. Two point charges 4 μC and 2 μC are separated by a distance 1 m in air. At what point on the line joining the two charges is the electric field intensity zero?

  12. Derive an expression for the work done in rotating a dipole through an angle θ in a uniform electric field.
    3 Marks Questions

  13. Show that, in a uniform electric field, a dipole experiences only a torque, but no net force. Derive an expression for the torque experienced by a dipole in a uniform electric field.

  14. Write three points of difference between mass and charge.

  15. An electric dipole of length 2 cm is placed with its axis making an angle 60 degrees with respect to a uniform electric field of 105 N/C. If it experiences a torque of 8 √3 Nm, calculate the
    (i) magnitude of charge on the dipole, and
    (ii) potential energy of the dipole.
    5 marks Questions

  16. Using Gauss' theorem, derive an expression for the electric field intensity at a point due to a uniformly charged spherical conducting shell when the point is
    (a) outside the sphere
    (b) on the sphere
    (c) inside the sphere


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