Physics

Problem

Which expression gives the magnitude of the force per unit length between two long, straight, parallel wires separated by a distance

r

and carrying currents

I_{1}

and

I_{2}

? a)

\displaystyle \frac{\mu_{0}}{4\pi}\,\frac{I_{1}I_{2}}{r^{2}}

\displaystyle \frac{\mu_{0}}{2\pi}\,\frac{I_{1}I_{2}}{r}

\displaystyle \frac{\mu_{0}}{2\pi}\,\frac{I_{1}I_{2}}{r^{2}}

\displaystyle \frac{\mu_{0}}{2\pi}\,\frac{I_{1}+I_{2}}{r}