Force between Two Parallel Current-carrying Conductors

The below rules govern the direction of the magnetic field round the current-carrying conductors.

1. Maxwell: If a right handed cork screw is turned so that it travels along the direction of the  current, the direction of the cork screw is the direction of the magnetic field.

2. Clenched Fist Rule: If the wire is grasped with the right hand so that the thumb point in the  direction of the current, the Clenched Fist direction is the direction of the magnetic field.

Case I: Two parallel current-carrying conductors with current in opposite directions.

Here, a repulsive force is created between the two conductors. Hence, they tend to move away  from each other.

Case II: Two parallel current-carrying conductors with current in the same direction.

Here, an attractive force is created between the two conductors. Hence, they tend to move towards each other.