Two long parallel conductors, kept at a dsitance d, carry currents `I_(1) and I_(2)` respectively. The mutual force acting between them is F. now the current in one is doubled and its direction is also reversed. If the distance of seperation between them is made 3d, what will be the force acting between the two conductors ?

Explanation

For unit of the conductors,
`F=(mu_(0))/(4pi)*(2I_(1)I_(2))/(d)`
If the current in the first conductor is doubled and its direction is reversed, it will be `-2I_(1)`.
`:.` In the second case,
`F'=(mu_(0))/(4pi)*(2(-2I_(1))I_(2))/(3d)=-(2)/(3) (mu_(0))/(d)*(2I_(1)I_(2))/(d)=-(2)/(3)F`