Suppose we want to verify the analogy between electrostatic and magnetostatic by an explicit experiment. Consider the motion of (i) electric dipole $\stackrel{\to }{\mathrm{p}}$ in an electrostatic field $\stackrel{\to }{\mathrm{E}}$ and (ii) magnetic dipole $\stackrel{\to }{\mathrm{M}}$ in a magnetic field $\stackrel{\to }{\mathrm{B}}$. Write down a set of conditions on $\stackrel{\to }{\mathrm{E}}$, $\stackrel{\to }{\mathrm{B}}$, $\stackrel{\to }{\mathrm{p}}$$\stackrel{\to }{\mathrm{M}}$ so that the two motions are verified to be identical. (Assume identical initial conditions).

Hint: The torque in both conditions should be the same.
Step 1: Now, suppose that the angle between M and B is $\mathrm{\theta }$.
Torque on magnetic dipole moment M in magnetic field B,

$\mathrm{\tau }$= MBsin$\mathrm{\theta }$
Step 2: Two motions will be identical, if;
pEsin$\mathrm{\theta }$ = MBsin $\mathrm{\theta }$
$⇒$        pE = MB                            ..(i)
But,        E = cB,
Step 3:
$\therefore$ putting this value in Eq. (i);
pcB = MB