Voltage induced by the rotating loop is sinusoidal in time with an angular frequency $\omega$ equal to that of the rotating loop, and its amplitude is equal to the produce of the surface area of the loop, the magnitude of the magnetic field generated by the magnet, and angular frequency $\omega$
$V_{emf}$ is also given by the general expression of Faraday’s law:
$$ V_{emf} = -\frac{d \Phi}{dt} = -\frac{d}{dt} \int _s B \cdot ds \text{ (total emf)} $$
$$ \oint _c H \cdot dl = I_c + \int _s \frac{\delta D}{\delta t} \cdot ds $$
$$ I_d = \int _S J_d \cdot ds \int _S \frac{\delta D}{\delta t} \cdot ds $$
