Question

A coil carrying a current I = 10 mA is placed in a uniform magnetic field so that its axis coincides with the field direction. The single-layer winding of the coil is made of copper wire with diameter d = 0.10 mm, radius of turns is equal to R = 30 mm. At what value of the induction of the external magnetic field can the coil winding be ruptured?

Answer 1

Each element of length dl experiences a force Bl dl. This causes a tension T in the wire.

For equilibrium,

where dα  is the angle subtended by the element at the centre. 

This must equals the breaking stress σ_m for rupture. Thus,