Question

two infinitely long parallel wires are at a distance of 1 metre both of them carry 2 ampere of current the force of attraction per unit length between the two wire is found to be K * 10-7 Newton per metre find k​

Answer 1

that's correct answer

Answer 2

Explanation:  Force per unit length between two infinity long parallel wires is given by,  

where, is permeability of vaccum or air,  are current through parallel wires respectively and d is the separation between wires.

here,  = 4π × 10^-7 Nm/A²

and d = 1m

so,  = 4π × 10^-7 × (2)²/(2π × 1)

= 2 × 10^-7 × 4

= 8 × 10^-7 N/m

but given, force per unit length is k × 10^-7 N/m

comparing both sides,

we get, k = 8