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
- Define electric flux.
- How is the force between two charges affected when dielectric constant of the medium in which they are placed increases?
- Name the physical quantity whose SI unit is NC-1
- Why two electric lines of force never intersect each other?
- Define dielectric constant of a medium.
- What is an ideal dipole?
- Write the SI unit of electric dipole moment.
- Calculate the number of electrons making a charge of -0.1 mC.
2 Marks questions
- Vehicles carrying inflammable materials have metallic ropes (or chains)touching the ground while in motion. Explain why is it necessary?
- Derive an expression for the electric field intensity at a distance ‘r’ from a point charge ‘q’
- 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?
- Derive an expression for the work done in rotating a dipole through an angle θ in a uniform electric field.
3 Marks Questions
- 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.
- Write three points of difference between mass and charge.
- 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
- 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