The diagram shows the magnetic field lines of a bar magnet. $A$ coil is moved from above the magnet to below it and then back to the original position. Which of the following graphs best represents the variation of magnetic flux $\Phi$ through the coil with time $t$?

Consider a closed loop $C$ in a magnetic field as shown in the figure. The flux passing through the loop is defined by choosing a surface whose edge coincides with the loop and using the formula $\phi = \sum \vec{B}_i \cdot d\vec{A}_i$. Now,if we choose two different surfaces $S_1$ and $S_2$ having $C$ as their edge,would we get the same answer for the magnetic flux? Justify your answer.

$A$ square coil of area $10^{-2} \ m^2$ is placed perpendicular to a uniform magnetic field of intensity $10^3 \ Wb/m^2$. The magnetic flux through the coil is ........ $Wb$.

$A$ circular disc of radius $0.2 \; m$ is placed in a uniform magnetic field of induction $\frac{1}{\pi} \; Wb/m^2$ in such a way that its axis makes an angle of $60^{\circ}$ with $\vec{B}$. The magnetic flux linked with the disc is..... $Wb$.

The adjoining figure shows two different arrangements in which two square wire frames are placed in a uniform constantly decreasing magnetic field $B$. The value of magnetic flux in each case is given by:

The net magnetic flux through any closed surface is