Obtain an expression for the force between two straight parallel conductor carrying current. Hence define ampere.

Explanation

`F = (mu_(0)I_(1)I_(2))/(2pi d)`
If `I_(1) = I_(2) = 1 A` and `d = 1m`, we get `F = (4pi xx 10^(-7))/(2pi) = 2 xx 10^(-7) Nm^(-1)`
ampere is defined as that current which when flowing in each of the two infinitely long parallel conductors 1m apart in free space will cause each conductor to experience a force of `2 xx 10^(-7) Nm^(-1)`.