A 2.4 mm - diameter copper wire carries a 37 A current (uniform across its cross section). Determine the magnetic field at the surface of the wire. Express your answer using two significant figures

We shall apply Ampere's circuital law to find out magnetic field. It is given as follows.

∫B. dl = μ₀ I, B is magnetic field, I is current, μ₀ is permeability.

Radius of the wire r = 1.2 x 10⁻³ m

magnetic field B will be circular in shape around the wire. If B is uniform

∫B. dl = B x 2πr

B x 2πr = μ₀ I

B = μ₀ I / 2πr

= 4π x 10⁻⁷ x 37 / 2πx1.2 x 10⁻³

= 10⁻⁷ x 2x37 / 1.2 x 10⁻³

= 61.67 x 10⁻⁴ T

= 62 x 10⁻⁴ T