Define SI unit of current in terms of the force between two parallel current carrying conductors.
(b) Two long straight parallel conductors carrying steady currents `I_(a)andI_(b)` along the same direction are separated by a distance d. How does one explain the force of attraction between them ? If a third conductor carrying a current `I_(c)` in the opposite direction is placed just in the middle of these conductors , find the resultant force acting on the third conductor.