Question

Two free parallel wires carrying currents in the opposite directions

• A. attract each other
• B. repel each other
• C. do not effect each other
• D. get rotated to be perpendicular to each other

Answer 1

Answer: (B)

When two infinitely long parallel conductors carrying current $I_1$ and $I_2$ are placed a distance $r$ apart, then force on the unit length of a conductor due to the other conductor is given by
$F=\frac{{\mu }_0}{4\pi }\cdot \frac{2I_1{I}_2}{r}$
The force is attractive, if current in two conductors is in same direction; and repulsive, if currents are in opposite directions.