Physics

Problem

Which of the following expressions gives the magnitude of the magnetic field

B

at a perpendicular distance

r

from a very long straight conductor carrying a steady current

I

? a)

B = \dfrac{\mu_0 I}{\pi r}

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

B = \dfrac{\mu_0 I}{4\pi r}

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