Q. A coil of $Cu$ wire (radius-$r$, self inductance-$L$) is bent in two concentric turns each having radius $\frac{r}{2}$. The self inductance now
A) $2L$
B) $L$
C) $4L$
D) $L/2$
Explanation
(a) $\because L \propto N^{2}r;\frac{L_{1}}{L_{2}} = \left( \frac{N_{1}}{N_{2}} \right)^{2} \times \frac{r_{1}}{r_{2}}$
$\Rightarrow \frac{L}{L_{2}} = \left( \frac{1}{2} \right)^{2} \times \left( \frac{r}{r/2} \right) = \frac{1}{2};L_{2} = 2L$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.