Two long conductors separated by a distance '$$\mathrm{d}$$' carry currents $$I_1$$ and $$I_2$$ in the same direction. They exert a force '$$F$$' on each other. Now the current in one of them is increased to two times and its direction is reversed. The distance between them is also increased to $$3 \mathrm{~d}$$. The new value of force between them is

A circular arc of radius '$$r$$' carrying current '$$\mathrm{I}$$' subtends an angle $$\frac{\pi}{16}$$ at its centre. The radius of a metal wire is uniform. The magnetic induction at the centre of circular arc is $$\left[\mu_0=\right.$$ permeability of free space]

A cylindrical magnetic rod has length $$5 \mathrm{~cm}$$ and diameter $$1 \mathrm{~cm}$$. It has uniform magnetization $$5.3 \times 10^3 \mathrm{~A} / \mathrm{m}^3$$. Its net magnetic dipole moment is nearly

Two parallel wires of equal lengths are separated by a distance of $$3 \mathrm{~m}$$ from each other. The currents flowing through $$1^{\text {st }}$$ and $$2^{\text {nd }}$$ wire is $$3 \mathrm{~A}$$ and 4.5 A respectively in opposite directions. The resultant magnetic field at mid point between the wires $$\left(\mu_0=\right.$$ permeability of free space)