Two parallel wires 1 m apart carry currents of 1 A and 3 A respectively in opposite directions. The force per unit length acting between these two wires is

Options

A. `6xx10^(-7) " N m"^(-1)` attractive
B. `6xx10^(-5) " N m"^(-1)` attractive
C. `6xx10^(-7) " Nm"^(-1)` repulsive
D. `6xx10^(-5) " Nm"^(-1)` repulsive

Answer

C

Explanation

The force per unit length acting between two parallel wires carrying currents `I_(1) and I_(2)` and placed a distance d apart is
` f = (mu_(0)I_(1)I_(2))/(2pid)`
Here , `I_(1) = 1 , I_(2) = 3 A , d = 1 m `
` mu_(0) = 4pi xx10^(-7) T " m A"^(-1)`
` :. f = ((4pi xx10^(-7) "T m " A^(-1))(1 A )(3 A))/(2pi(1m)) `
` = 6 xx 10^(-7) " N m"^(-1)`
As the currents are in opposite directions , so f is repulsive