Question

Formula of magnetic field in solenoid

Answer 1

B = μ₀ n I

Answer 2

For an ideal long solenoid (where end effects are negligible), by applying Ampère’s circuital law along an appropriate loop, the magnetic field inside is uniform and given by

$$B = \mu_0 n I,$$

where • $\mu_0$ is the permeability of free space, • $n$ is the number of turns per unit length ($n = \frac{N}{L}$), and • $I$ is the current through the solenoid.