At some location on earth, the horizontal component of earth’s magnetic field is 18 × 10^–6 T. At this location, magnetic needle of length 0.12 m and pole strength 1.8 Am is suspended from its mid-point using a thread, it makes 45^o angle with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is -

A magnet of total magnetic moment 10^-2 $${\widehat i}$$ A-m² is placed in a time varying magnetic field, B$${\widehat i}$$ (cos $$\omega t$$) where B = 1 Tesla and $$\omega $$ = 0.125 rad/s. The work done for reversing the direction of the magnetic moment at t = 1 second, is -

A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns, and carrying a current of 5.2 A. The corecivity of the bar magnet is :

The $$B$$-$$H$$ curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solended with $$1000$$ turns/cm. The current that should be passed in the solended to demagnetise the ferromagnet completely is :