Which one of the following expressions gives the magnitude of the magnetic field at a…

PHYSICS · Single correct · AP · Physics C: Electricity and Magnetism · Magnetic Fields and Electromagnetism · Magnetic Fields and Electromagnetism

Problem

Which one of the following expressions gives the magnitude of the magnetic field at a distance

r

from an infinitely long straight conductor carrying a steady current

I

in air (symbols have their usual meaning)? (a)

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

(b)

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

(c)

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

(d)

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