A solid wire with a radius of 10 cm carries a 5.0 A current that is uniformly distributed across its cross section. Determine the magnetic field B at a point located at a distance of 20 cm from the axis.

Step-by-step solution

Using Ampere's circuital law, the magnetic field at a point outside a long straight current-carrying wire is given by B = ₀ I 2 r Given that the point is at a distance r = 20 cm = 0.2 m from the axis, which is greater than the radius of the wire ( R = 10 cm ), the point lies outside the wire. Substituting the given values I = 5.0 A and r = 0.2 m : B = 4 10⁻⁷ 5.0 2 0.2 B = 2 10⁻⁷ 5.0 0.2 B = 10 10⁻⁷ 0.2 B = 50 10⁻⁷ T B = 5.0 10⁻⁶ T = 5.0 T