Question

The figure shows a conducting ring of radius $R$. A uniform steady magnetic field $B$ lies perpendicular to the plane of the ring in a circular region of radius $r(<R)$. If the resistance per unit length of the ring is $\lambda$, then the current induced in the ring when its radius gets doubled is

• A. $\frac{BR}{\lambda }$
• B. $\frac{2BR}{\lambda }$
• C. $zero$
• D. $\frac{B{r}^2}{4R\lambda }$

Answer 1

The correct option is C $zero$

Radius of the region where the magnetic field exists is less than the radius of the ring.

Thus even when the radius of the ring increases the flux through it doesn't change, and there is no induced emf in the ring.