Two long conductors, separated by a distance `d` carry current `I_(1) and I_(2)` in the same direction . They exert a force `F` on each other. Now the current in one of them is increased to two times and its direction is reversed . The distance is also increased to `3d`. The new value of the force between them is

Options

A. `-(F)/(3)`
B. `(F)/(3)`
C. `(2F)/(3)`
D. `(-2F)/(3)`

Answer

D

Explanation

Force between two conductors,
`F prop=(i_(1)i_(2))/(d)`
When `l_(2)` is changed to `2 l_(1)` and d is changed to 3d.
`:. F prop=((2i_(1))(i_(2)))/(3d)prop(2)/(3)F`
As direction of current is reversed so,
`F'=-2F//3`