# 20 (b). A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of $45 \degree$ with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east.  The current in the coil is reversed, and the coil is rotated about its vertical axis by an angle of $90 \degree$ in the anticlockwise sense looking from above. Predict the direction of the needle. Take the magnetic declination at the places to be zero.

When the current in the coil is reversed and the coil is rotated about its vertical axis by an angle of $90 \degree$ in the anticlockwise sense looking from above, then the needle will reverse its direction. The new direction will be from east to west.