Two identical bar magnets are fixed with their centers at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure


The force on the charge Q is

Electromagnets are made of soft iron because soft iron has

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 24 microtesla. When a horizontal field of 18 microtesla is produced opposite to the earth's field by placing a current carrying wire, the new time period of magnet will be

A bar magnet having a magnetic moment of 2 $$ \times $$ 10⁴ J T^$$-$$1 is free to rotate in a horizontal plane. A horizontal magnetic field B = 6 $$ \times $$ 10^$$-$$4 T exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction 60^o from the field is