Question

A uniform magnetic field of induction B is confined in a cylindrical region of radius R. If the field is increasing at a constant rate of $\frac{dB}{dt}=\alpha T\frac{T}{s}$, then the intensity of the electric field induced at point P, distant r from the axis as shown in the figure is proportional to :

• A. $r^3$
• B. $r^2$
• C. $r$
• D. $\frac{1}{r}$

Answer 1

The correct option is C $r$

Consider an imaginary circle with 'r' as radius, then
$E\left(2\pi r\right)=\frac{dB}{dt}\pi r^2$