The coercivity of a magnet is $$5 \times 10^3 \mathrm{~A} / \mathrm{m}$$. The amount of current required to be passed in a solenoid of length $$30 \mathrm{~cm}$$ and the number of turns 150, so that the magnet gets demagnetised when inside the solenoid is ________ A.

The horizontal component of earth's magnetic field at a place is $$3.5 \times 10^{-5} \mathrm{~T}$$. A very long straight conductor carrying current of $$\sqrt{2} \mathrm{~A}$$ in the direction from South east to North West is placed. The force per unit length experienced by the conductor is __________ $$\times 10^{-6} \mathrm{~N} / \mathrm{m}$$.

The magnetic potential due to a magnetic dipole at a point on its axis situated at a distance of $$20 \mathrm{~cm}$$ from its center is $$1.5 \times 10^{-5} \mathrm{~T} \mathrm{~m}$$. The magnetic moment of the dipole is _________ $$A \mathrm{~m}^2$$. (Given : $$\frac{\mu_o}{4 \pi}=10^{-7} \mathrm{Tm} A^{-1}$$ )

A compass needle oscillates 20 times per minute at a place where the dip is $$30^{\circ}$$ and 30 times per minute where the dip is $$60^{\circ}$$. The ratio of total magnetic field due to the earth at two places respectively is $$\frac{4}{\sqrt{x}}$$. The value of $$x$$ is