Opposite currents in parallel wires

Introduction:
When two parallel wires carry currents in the opposite direction, there is a magnetic interaction between the two wires. This interaction can result in either attraction or repulsion between the wires. Let's explore the possible scenarios.

Explanation:
When two parallel wires carry currents in opposite directions, the magnetic fields produced by the currents interact with each other. This interaction is governed by Ampere's law and the right-hand rule.

Direction of magnetic fields:
The magnetic field produced by a current-carrying wire can be determined using the right-hand rule. If we point the thumb of our right hand in the direction of the current, the fingers will curl in the direction of the magnetic field.

Case 1: Attraction:
When two parallel wires carry currents in opposite directions, the magnetic fields produced by the currents will have the same direction between the wires and opposite directions outside the wires. According to Ampere's law, these magnetic fields will exert a force on each other, resulting in an attractive force between the wires. This is because the magnetic field lines of one wire will "link" with the magnetic field lines of the other wire, causing the wires to be attracted to each other.

Case 2: Repulsion:
If the currents in the parallel wires are relatively strong, the magnetic fields produced by the currents may be strong enough to overcome the attractive force and result in repulsion. This can occur when the currents are very high or the wires are placed very close to each other.

Case 3: Neither attract nor repel:
If the currents in the parallel wires are very weak, the magnetic fields produced by the currents may not be strong enough to cause any noticeable attraction or repulsion between the wires. In this case, the wires will not attract or repel each other.

Conclusion:
When two parallel wires carry currents in opposite directions, they can either attract or repel each other, depending on the strength of the currents and the distance between the wires. If the currents are relatively weak, there may not be any noticeable attraction or repulsion between the wires. However, if the currents are strong enough, the wires will repel each other. Therefore, the correct answer is option 'B': the wires repel each other.