Question

If the currents in two straight current-carrying conductor, distant d apart, are $i_1$ and $i_2$ respectively in the same direction then they will

• A. rotate about a central axis
• B. attract each other
• C. repel each other
• D. neither attract not repel each other

Answer 1

The correct option is B attract each other

Force experienced by one current carrying conductor due to another parallel straight conductor per unit length is,
$F=\frac{{\mu }_0{i}_1{i}_2}{2\pi r}$
where, variables have their usual meanings.
If the current flowing through the conductors is in the same direction they will attract each other. If current flows in opposite direction through both the conductors then they will repel each other.