Question

Figure shows a circular area of radius R where a uniform magnetic field $\vec{B}$ is going into the plane of paper and increasing in magnitude at a constant rate. In that case, which of the following graphs, drawn schematically, correctly shows the variation of the induced electric field E(r)?

• A.
• B.
• C.
• D.

Answer 1

Answer: (D)

Answer 2

$B = B _{0} t$
$r >\, R$
$\phi \bar{\varepsilon} \cdot de =\frac{ d \phi}{ dt }$
$\Rightarrow \varepsilon(2 \pi r )= B \pi r ^{2}$

$e \propto r$
$r >\, R$
$\varepsilon(2 \pi r )= B \pi R ^{2}$
$\varepsilon \propto \frac{1}{r}$