A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is

In a coil of resistance 10 $$\Omega $$, the induced current developed by changing magnetic flux through it, is shown in figure as a function of time. The magnitude of change in flux through the coil in weber is

A coil of resistance 400 $$\Omega $$ is placed in a magnetic field. If the magnetic flux $$\phi $$ (Wb) linked with the coil varies with time t (sec) as $$\phi = 50{t^2} + 4$$.

The current in the coil at t = 2 sec is

The current $$i$$ in a coil varies with time as shown in the figure. The variation of induced emf with time would be