RE-NEET 2026 Physics Inductance MCQ Question

The inductance $L$ of a long solenoid is given by the formula:

$$L = \mu_0 n^2 \pi r^2 l$$

where $\mu_0$ is the permeability of free space, $n$ is the number of turns per unit length, $r$ is the radius, and $l$ is the length of the solenoid. This formula arises from the magnetic field inside the solenoid and the energy stored in the magnetic field.

The other options fail because they either misrepresent the geometric factors (like $2\pi$ or lack of $\pi$) or do not correctly account for the relationship between the solenoid's dimensions and its inductance.