Question

A long straight wire carries a current of 35 A. What is the magnitude of the field B at a point 20 cm from the wire?

Answer 1

Current in the wire, I = 35 A

Distance of a point from the wire, r = 20 cm = 0.2 m

Magnitude of the magnetic field at this point is given as:

B = `(mu_0I)/(2pix)`

B `= (4pixx10^-7 xx35)/(2xxpixx0.2)`

B = `35xx10^-7/0.1   ...0.1xx10/10 = 1/10 = 10^-1`

B = 35 × 10^–6 T

= 3.5 × 10^–5 T

Hence, the magnitude of the magnetic field at a point 20 cm from the wire is 3.5 × 10^–5 T.