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

Options

A. 4
B. 3
C. 2
D. 1

Answer

C

Explanation

According to the equation
`(mu_(0))/(2pir) ((1)/(i_(2))-(1)/(i_(1)))=10xx10^(-6)`
and `(mu_(0))/(2npi)((1)/(i_(2))-(1)/(i_(1)))=30xx10^(-6)`
On dividing Eq. (ii), (ii) we get
`(i_(1)+i_(2))/(i_(1)-i_(2))`
Solving this equation. we get
`(i_(1))/(i_(2))=2`