Question

Two parallel wires carrying equal currents `i_(1)` and `i_(2)` with `i_(1)gti_(2)`. When the current are in the same direction, the `10 mT`. If the direction of `i_(2)` is reversed, the field becomes `30 mT`. The ratio `i_(1)//i_(2)` is
A. `4`
B. `3`
C. `2`
D. `1`

Answer 1

Correct Answer - C
`10mT=(mu_(0))/(2pi(r//2)) (i_(1)-i_(2))`
`30 mT=(mu_(0))/(2pi(r//2)) (i_(1)+i_(2))`
Dividing : `i_(1)//i_(2)=2`