Following Questions of a paragraph has only one correct answer amongthe four choices(A), (B), (C) and (D).

A point charge Q is moving in a circular orbit of radius R in the x-y plane with an angular velocity $$\omega$$ This can be considered as equivalent to a loop carrying a steady current $$\frac{Q \omega}{2 \pi}$$. A uniform magnetic field along the positive z-axis is now switched on, which increases at a constant rate from 0 to B in one second. Assumethat the radius of the orbit remains constant. The application of the magnetic field induces an emf in the orbit. The induced
emf is defined as the work done by an induced electric field in moving a unit positive charge around a closed loop. It is knownthat, for an orbiting charge, the magnetic dipole momentis proportional to the angular momentum with a proportionality constant $$\gamma$$