Two long,parallel wires carry currents of different magnitudes.If the current in one of the wires is doubled and the current in the other wire is halved,what happens to the magnitude of the magnetic force that each wire exerts on the other?
A)It is doubled.
B)It stays the same.
C)It is tripled.
D)It is quadrupled.
E)It is reduced by a factor of two.

Question

Quizplus · Accepted Answer

The magnetic force between two parallel wires is given by the expression F = (μ₀I₁I₂L)/(2πr), where I₁ and I₂ are the currents, L is the length of the wires, r is the distance between them, and μ₀ is the magnetic constant. 
If we double the current in one wire (I₁→2I₁) and halve the current in the other wire (I₂→(1/2)I₂), the force expression becomes F' = (μ₀ x 2I₁ x (1/2)I₂ x L)/(2πr) = F. 
Therefore, the magnitude of the magnetic force that each wire exerts on the other stays the same.

Two Long,parallel Wires Carry Currents of Different Magnitudes