Numerical based on electric charge ,electric field .

Numerical based on electric charge ,electric field .

Numerical based on electric dipole ( electric field at axial and equatorial point, torque and potential energy stored in dipole )-

  1. Two charges + 30μc and -30μc are placed 1cm apart . calculate electric field at a point on the the axial and equatorial line at a distance of 20 cm from the centre of the dipole .

Ans- 6.25 x 105 N/C and 3,25 x 105‑ N/C .

  1. An electric dipole of dipole moment 4 x 10-5 C-m is placed in uniform electric field of 103 N/C making an angle of 300 with the direction of field . Determine the torque exerted by the electric field on the dipole.    Ans- 2 x 10-8Nm .
  2. An electric dipole is placed at an angle of 600 with an electric field of magnitude 4 x 105 N /C . It experience a torque of 8√3 Nm . If the length of the dipole is 2cm , determine the magnitude of either charge of the dipole . Ans –  2 x 10-3 C .
  3. An electric dipole of length 10cm having charges of magnitude 6 x 10-3 C , placed at 300 with respect to a uniform electric field experience a torque of magnitude 6√3 N-m . Calculate (i) magnitude of the field and (ii) potential energy of the dipole . Ans- 2√3x 104; -18J
  4. An electric dipole consist of two opposite charges of magnitude q=1×10-6C separated by 2.0 cm . The dipole is placed in an external electric field of 1×105 N/C . What maximum torque does the field exert on the dipole ? How much work must an external agent to do turn the dipole end for end , starting from position of alignment ( ϴ=00 ) . Ans- 2×10-3 N-m ; 4×10-3J .
  5. (i)Two point charges 4Q and Q are separated by 1m in air at what point on the line joining the two charges the electric field intensity is zero. (ii) Two identical metallic sphere A and B having charges +4Q and -10Q are kept at a certain distance apart . A third identical uncharged sphere C is first placed in contact with sphere A and then with sphere B . Spheres A and B are then brought in contact and then separated . Find the charges on the sphere A and B .

7.Calculate the amount of work done in turning an electric dipole of dipole moment 3×108 C-m from its position of unstable equilibrium to stable equilibrium, in a uniform electric field of intensity 103N/c.

8.The sum of two point charges is 7µc they repel each other with a force of 1N when kept 30 cm apart in free space , calculate the value of each charge.

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