Chapter-4|Moving Charges and Magnetism| NCERT 12th Physics:
Force Between Two Parallel Current Carrying Conductors:
Let we consider two parallel infinite long straight conductors.
Note: Two linear parallel conductors carrying current in the same direction attract each other, while carrying in opposite direction they repel to each other.
Definition of Ampere:
1 Ampere: 1 ampere is the current which flow through each of two parallel infinite wires placed at a distance of 1 metre apart produces an attractive or repulsive force per unit length between wire of 2×10⁻⁷ N/m.
sir expalin equation 1