A long, straight wire (radius = 2.0 mm) carries a current of 2.0 A distributed uniformly over a cross section perpendicular to the axis of the wire. What is the magnitude of the magnetic field at a distance of 1.0 mm from the axis of the wire?

Answer: The magnetic field is 4*10^-4T

Explanation:

Using the magnetic field equation

B=μI/2πr

B = magnetic field = ?

l = current in the wire=2.0A

r = distance from the axis of wire=1.0mm = 0.001m

μ=magnetic permeability = 4π*10^-7N/m

B = (4π*10^-7 * 2.0) / (2π * 0.001)

B = 4*10^-4T

Therefore the magnetic field is 4*10^-4T