Moving Charges and Magnetism

As, we know that, force on a moving charge particle.

$\therefore F=Bqv\sin\theta$

Hence, F will be zero, if any of the parameter of above formula equals zero.

$\therefore$ Force on a charge at rest will be zero.

Given, radius of hollow cylinder = R

Current = i

Distance from axis = r

Let magnetic field be B.

$\because$ No current is passing through region r < R

and magnetic field $(B)=\frac{1}{2\pi}\frac{\propto_0I}{r}$

$\begin{aligned} \text{So,} \\& B(r < R)=0 \\ & B(r=R)=\frac{1}{2 \pi} \frac{\propto_0 I}{R} \\ \text {and}\\& B(r>R)=\frac{1}{2 \pi} \frac{\propto_0 I}{r} \end{aligned}$

So, these variations are correctly shown as below.