Two parallel wires carrying equal currents of 10 A attract each other with a force of 1 mN. If both currents are doubled, the force of attraction will be:
A) 1 mN
B) 4 mN
C) 0.5 mN
D) 0.25 mN
E) 2 mN

Question

Quizplus · Accepted Answer

The force of attraction between the two wires is given by the formula:

F = (μ₀*I₁*I₂*L)/(2π*r)

where F is the force of attraction, μ₀ is the permeability of free space, I₁ and I₂ are the currents, L is the length of the wires, and r is the distance between the wires.

Since the currents in both wires are doubled to 20 A, the force of attraction between the wires will be:

F' = (μ₀*20 A*20 A*L)/(2π*r)

= 4*(μ₀*10 A*10 A*L)/(2π*r)

= 4*F

Therefore, the force of attraction between the wires will be 4 times the original force, which is 1 mN. So the answer is B.

Two Parallel Wires Carrying Equal Currents of 10 a Attract