The radius of a coil of $N$ turns is $R$. If the plane of the coil is placed parallel to a uniform magnetic field $B$,then the flux linked with the coil is:

Assertion: The magnetic field lines are continuous and form closed loops.
Reason: Magnetic monopole does not exist.
The correct option among the following is

$A$ circular disc of radius $20 \text{ cm}$ is placed in a uniform magnetic field of induction $\frac{7}{22} \text{ Wb/m}^2$ in such a way that its axis makes an angle of $60^{\circ}$ with $\vec{B}$. The magnetic flux linked with the disc is $(\cos 60^{\circ} = 0.5)$ (in $\text{ Wb}$)

The magnetic flux linked with a closed coil is increased to a maximum value in $2 \,s$ and its relation with time is $\phi = at^2 + bt + c$. Then the relation between $a, b$ and $c$ is:

Imagine rolling a sheet of paper into a cylinder and placing a bar magnet near its end as shown in the figure. What can you say about the sign of $\vec B \cdot d\vec A$ for every area element $d\vec A$ on the surface of the cylinder?

Explain Gauss's law for magnetism.