Two parallel, long wires carry current `i_(1)` and `i_(2)` with`i_(1)gti_(2)`. When the currents are in the same direction, the magnetic field at a point midway between the wires is `30 muT`. If the direction of `i_(1)` is reversed , the field becomes `90muT`. The ratio `i_(1)//i_(2)` is

Options

A. `1//2`
B. `2`
C. `2//3`
D. `3//2`

Answer

D

Explanation

`(mu_(0))/(2pir)(i_(1)-i_(2))=6xx10^(-6)` ……..i
`(mu_(0))/(2pir)(i_(1)+i_(2))=3xx10^(-5)`…….ii
On solving and ii we get `(i_(1))/(i_(2))=3/2`