A 100 turn closely wound circular coil of radius `10cm` carries a current of `3*2A`. (i) What is the field at the centre of the coil? (ii) What is the magnetic moment of this arrangement? The coil is placed in a vertical plane and is free to rotate about a horizontal axis which coincides with its diameter. A uniform magnetic field of `2T` in the horizontal direction exists such that initially the axis of the coil is in the direction of the field. The coil rotates through an angle of `90^@` under the influence of the magnetic field. (iii) What are the magnitudes of the torques on the coil in the initial and final positions? (iv) What is the angular speed acquired by the coil when it has rotated by `90^@`? The moment of inertia of the coil is `0*1kgm^2`.

Options

A. `20 s^(-1)`
B. `30 s^(-1)`
C. `40 s^(-1)`
D. `60 s^(-1)`

Answer

a