The magnetic flux through a coil is $4 \times 10^{-4} \ Wb$ at time $t=0$. It reduces to $30 \%$ of its original value in time $t$ seconds. If the e.m.f. induced in the coil is $0.56 \ mV$,then the value of $t$ is: (in $s$)

$A$ circular coil of area $2 \text{ cm}^2$ is placed in a magnetic field of $3 \text{ T}$ perpendicularly. The coil has $10$ turns and $5 \text{ } \Omega$ resistance. Now,the coil is removed from the magnetic field in $0.2 \text{ s}$. The value of induced charge flowing through the coil is . . . . . . .

$A$ coil having $500$ square loops each of side $10 \ cm$ is placed normal to a magnetic flux which increases at a rate of $1 \ T s^{-1}$. The induced emf is (in $V$)

Assertion: An $emf$ $\vec{E}$ is induced in a closed loop where magnetic flux is varied. The induced $\vec{E}$ is not a conservative field.
Reason: The line integral $\oint \vec{E} \cdot d\vec{l}$ around the closed loop is nonzero.

The figure shows planar loops of different shapes moving out of or into a region of a magnetic field which is directed normal to the plane of the loop away from the reader. Determine the direction of induced current in each loop using Lenz's law.

The figure shows a conducting loop placed in a magnetic field. The magnetic flux through the loop changes according to the equation $\phi = 5t - 10t^2$. What is the direction and magnitude of the induced current at $t = 0.25\, s$?