Using the concept of force between two infinitely long parallel current carrying conductors, define one ampere of current between two infinitely long parallel current carrying conductors, define one ampere of current.

Explanation

`F_(ba)=(mu_(0)I_(a)I_(b))/(2pid)`
`F_(ba)` represent the magnitude of the force per unit length.
This expression of force is also used to define the Ampere `(A)`,which is one of the seven `S.I` base units .The Ampere is the value of that steady current which, when maintained in each of the two long, stright , parallel conductor of negligible cross section, and placed one meter apart in vacuum, would produce of each of these conductor a force equal to `2xx10^(-7)` Newtons per meter of length.
`F_(ba)=(mu_(0)I_(a)I_(b))/(2pid)`