Q. A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of $2\, \sec$ in earth's horizontal magnetic field of $6$ microtesla. When a horizontal field of $18$ microtesla is produced in same direction of field by placing a current carrying wire, the new time period of magnet will be :-
Moving Charges and Magnetism
Solution: