To induce an $e.m.f.$ in a coil, the linking magnetic flux

The magnetic flux (in weber) in a closed circuit of resistance $20 \ \Omega$ varies with time $t$ (in seconds) according to the equation $\phi = 5t^2 - 6t + 9$. The magnitude of the induced current at $t = 0.2 \ s$ is: (in $A$)

State and explain Faraday's law of electromagnetic induction.

Magnetic flux in a circuit containing a coil of resistance $2\,\Omega$ changes from $2.0\,Wb$ to $10\,Wb$ in $0.2\,s$. The charge passed through the coil in this time is......$C$

$A$ circular loop of radius $7 \ cm$ is placed in a uniform magnetic field of $0.2 \ T$ directed perpendicular to the plane of the loop. The loop is converted into a square loop in $0.5 \ s$. The $EMF$ induced in the loop is . . . . . . $mV$.

$A$ metallic ring is dropped down, keeping its plane perpendicular to a constant and horizontal magnetic field. The ring enters the region of magnetic field at $t = 0$ and completely emerges out at $t = T \, \text{sec}$. The current in the ring varies as