Question

What is the magnetic field at the ends (edge) of a long solenoid carrying current \(I\)?

Options

• \(B = 0\)

• \(B = \frac{\mu_0 n I}{2}\)

• \(B = \mu_0 n I\)

• \(B = \mu_0 \mu_r n I\)

Answer 1

At the ends (edge) of a long solenoid, the magnetic field is \(B = \frac{\mu_0 n I}{2}\), which is exactly half the value at the center. The reason is that only half the turns contribute to the field at the edge, unlike the interior where the superposition of all turns gives \(B = \mu_0 nI\).