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)

repel each other

Answer 2

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
$F=\frac{\mu_{0}}{4 \pi} \cdot \frac{2 I_{1} I_{2}}{r}$
The force is attractive, if current in two conductors is in same direction; and repulsive, if currents are in opposite directions.