An expression for the magnetic field strength strength B at the point between the capacitor plates indicates in figure express B in terms of the rate of change of the electric field strength ie, dE/dt between the plates
Answer & explanation
Correct answer: option 2
$B =\frac{\mu_0}{4\pi}\frac{2i_D}{r}=\frac{\mu_0}{4\pi}×ε_0\frac{d\phi_E}{dt}$
$ =\frac{\mu_0}{2\pi}\frac{2i_D}{r}=\frac{\mu_0}{4\pi r}\frac{2}{r}×ε_0\frac{d\phi_E}{dt}$
$=\frac{\mu_0ε_0\pi r^2 dE}{2\pi rdt}=\frac{\mu_0ε_0r}{2}\frac{dE}{dt}$