Physics

Problem

Which one of the following expressions gives the magnitude of the magnetic field inside a long, tightly-wound air-cored solenoid carrying a current

I

with

n

turns per unit length? a)

B = \dfrac{\mu_0 n I}{2\pi}

B = \dfrac{\mu_0 n I}{2}

B = \mu_0 n I

B = \dfrac{\mu_0 n^{2} I}{2}