Question
A steady current $\left(I_1\right)$ flows through a long straight wire. Another wire carrying steady current $\left(I_2\right)$ in the same direction is kept close and parallel to the first wire. Show with the help of a diagram how the magnetic field due to the current $\mathrm{I}_1$ exerts a magnetic force on the second wire. Write the expression for this force.
$\text{F}_{12} = \text{I}_{2}\text{IB}_{1}$
