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

     
1. $2$
2. $6$
3. $4$
4. $8$

A coil of resistance $400~\Omega$ is placed in a magnetic field. The magnetic flux $\phi~\text{(Wb)}$ linked with the coil varies with time $t~\text{(s)}$ as $\phi=50t^{2}+4.$ The current in the coil at $t=2~\text{s}$ is:
1. $0.5~\text{A}$
2. $0.1~\text{A}$
3. $2~\text{A}$
4. $1~\text{A}$

The figure shows planar loops of different shapes moving out of or into a region of a magnetic field which is directed normally to the plane of the loop away from the reader. Then:

A conducting circular loop is placed in a uniform magnetic field, $B=0.025~\text{T}$ with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of $1~\text{mm s}^{-1}$. The induced emf, when the radius is $2~\text{cm}$, is:
1. $2\pi ~\mu\text{V}$
2. $\pi ~\mu\text{V}$
3. $\dfrac{\pi}{2}~\mu\text{V}$
4. $2 ~\mu \text{V}$