Two long parallel straight conductors carry current `i_(1)` and `i_(2)(i_(1)gti_(2))`. When the currents are in the same directions, the magnetic field at a point midway between the wires is `20muT`. If the direction of `i_(2)` is reversed, the field becomes `50muT`. The ratio of the current `i_(1)//i_(2)` is :

Options

A. `5//2`
B. `7//3`
C. `4//3`
D. `5//3`

Answer

B

Explanation

`B=(mu_(0))/(2pi(d//2))(i_(1)-i_(2))=20" "," "(mu_(0))/(2pi(d//2))(i_(1)+i_(2))=50`
`(i_(1)-i_(2))/(i_(1)+i_(2))=(2)/(5)`Treading`(i_(1))/(i_(2))=x" "," "x=(7)/(3)`