Question

What is the magnetic field on the equatorial line of a short bar magnet?

Options

• \[B_{\mathrm{eq}}=\frac{\mu_0}{4\pi}\frac{m}{r^3}\]

• \[B_{\mathrm{eq}}=-\frac{\mu_0}{4\pi}\frac{m}{r^3}\]

• \[B_{\mathrm{eq}}=-\frac{\mu_0}{4\pi}\frac{m}{r^2}\]

• \[B_{\mathrm{eq}}=-\frac{1}{4\pi\epsilon_0}\frac{m}{r^3}\]

Answer 1

On the equatorial line, the stated field is \[B_{\mathrm{eq}}=-\frac{\mu_0}{4\pi}\frac{m}{r^3}\]. The negative sign specifies its direction relative to the magnetic dipole moment vector.