Question

5. Use Ampére's law to determine the magnetic field strength... a. a distance r away from an infinitely long current carrying wire b. anywhere on either side of an infinite, flat sheet with a surface current density σ c. inside a solenoid with n turns per unit length

Answer 1

a)

consider a circular closed loop of radius "r" around a current carrying wire. let the current in the wire is "i"

using ampere's law

B $\oint$dl = $\mu$_o i

B (2$\pi$r) = $\mu$_o i

B = $\mu$_o i/(2$\pi$r)