(a) Derive the expression for the force acting between two long parallel current carrying conductors. Hence, define 1 A current.
(b) A bar magnet of dipole moment 3 Am2 rests with its centre on a frictionless pivot. A force F is applied at right angles to the axis of the magnet, 10 cm from the pivot. It is observed that an external magnetic field of 0.25 T is required to hold the magnet in equilibrium at an angle of with the field. Calculate the value of F. How will the equilibrium be effected if F is withdrawn ?
a)
Ampere is that value of steady-state current, which when maintained in each of the very two long, straight, parallel conductors of negligible cross-section and placed 1m apart in a vacuum produces force on each conductor.
b) At equilibrium
Restoring Torque = Deflecting Torque
The magnet oscillates for some time but finally aligns along the original direction of the external magnetic field.