A copper rod $$A B$$ of length $$l$$ is rotated about end $$A$$ with a constant angular velocity $$\omega$$. The electric field at a distance $$x$$ from the axis of rotation is

A strong magnetic field is applied on a stationary electron. Then, the electron

Two parallel wires in free space are $$10 \mathrm{~cm}$$ apart and each carries a current of $$10 \mathrm{~A}$$ in the same direction. The force exerted by one wire on the other [per unit length] is

A toroid with thick windings of $$N$$ turns has inner and outer radii $$R_1$$ and $$R_2$$, respectively. If it carries certain steady current $$I$$, the variation of the magnetic field due to the toroid with radial distance is correctly graphed in