Two long parallel conductors carry currents `i` and `2I` in the same direction. The magnetic induction at a point exactly mid way between them is `B`. If the current in the first conductor is reversed in direction, the magnetic induction at the same point will be

Options

A. `B//3`
B. `2B`
C. `3B`
D. `B//2`

Answer

3

Explanation

In the first case the two fields are in opposite directions and take the difference as the resultant field. In the next case, the two fields are in the same direction and add up.