A rectangular coil of 100 turns has length 5 cm and width 4 cm. it is placed with its plane parallel to a uniform magnetic field and a current of 2 A is sent through the coil. Find the magnitude of the magnetic field B, if the torque acting on the coil is `0.2 Nm^(-1).`

Options

A. `0.5 T`
B. `0.6 T`
C. `0.4 T`
D. zero

Answer

A

Explanation

`tau = |vec(tau)| = MB sin theta = N i A B sin 90^(@) = N i A B = N i l b B`
`B = (tau)/(N i l b) = (0.2)/(100 xx 2 xx 5 xx 4 xx 10^(-4)) = 0.5 T`