Two electrons, $$e_1$$ and $$e_2$$ of mass $$m$$ and charge $$q$$ are injected into the perpendicular direction of the magnetic field $$B$$ such that the kinetic energy of $$e_1$$ is double than that of $$e_2$$. The relation of their frequencies of rotation, $$f_1$$ and $$f_2$$ is

A wire of length $$L$$ metre carrying a current $$I$$ ampere is bent in the form of a circle. Magnitude of its magnetic moment is

What is the net force on the square coil?

In a co-axial, straight cable, the central conductor and the outer conductor carry equal currents in opposite directions. The magnetic field is zero