Three long, straight wires are carrying currents that have the same magnitude. In C the current is opposite to that in A and B. The wires are equally spaced. Each wire experiences a net force due to the other two wires.
Which wire experiences a net force that has the greatest magnitude?

(b) B

Explanation:

The direction of force on a current carrying wire in a magnetic field can be found using the right hand rule, which states that-"stretch the thumb in the direction of the current, and point the fingers in the direction of magnetic field. The direction of palm will then give the direction of force on the wire

On wire B the forces due to A and C act in the same direction and so strengthen each other. they get added up because the forces act in the same direction.

on wires A and C the forces (due to B and C and A and B

respectively) act in opposite directions and therefore tend to cancel out.

unlike poles attract