Question

What is the magnetic field at the centre of a coil of \(N\) tightly wound turns, radius \(R\), and current \(I\)?

Options

• \(B_0=\frac{\mu_0 I R}{2N}\)

• \(B_0=\frac{\mu_0 I}{2NR}\)

• \(B_0=\frac{\mu_0 N I}{2R^2}\)

• \(B_0=\frac{\mu_0 N I}{2R}\)

Answer 1

Each tightly wound turn contributes the field of one loop at the centre. The field therefore multiplies by the number of turns, giving \(B_0=\frac{\mu_0 N I}{2R}\).