Two very long conducting wire are kept at a distance 4 cm from each other in vacuum. Currents flowing through the wires are 25A and 5A, respectively. Find the length of each conductor, which experiences a force of 125 dynes ?

Explanation

Here, `I_(1)=25A,I_(2)=5A, r=4 cm=0.04 cm`
So, the force acting per unit length of the wire,
`F=F(mu_(0))/(4pi)*(2I_(1)I_(2))/(r)=(4pixx10^(-6))/(4pi)*(2xx25xx5)/(0.04)`
`=625xx10^(-6)N*m^(-1)`
`:.` Fow 125 dyn or `125xx10^(-5)N` force, the effective lenght of each wire,
`l=(125xx10^(-5))/(625xx10^(-6))=2m`