Two parallel wires carry currents of `10 A` and `40 A` in opposite directions.Another wire carrying a current antiparallel to `10 A` is placed midway between the two wires.The magnetic force on it will be

Options

A. towards `20A`
B. towards `40 A`
C. zero
D. perpendicular to the plane of the currents

Answer

B

Explanation

`F_(1)=(mu_(0)(10xx20))/(2pil)`
`F_(2)=(mu_(0)(20xx40))/(2pil)`
`F_(1)` and `F_(2)` both points in the same direction towards `40 A` wire.