Two parallel conductors are carrying currents in the opposite direction.The currents are non-zero and not necessarily equal.The magnitude of the magnetic field midway between them is 40 μT.If one of the currents then has its direction reversed,what is the resulting magnitude of the magnetic field midway between them?
A)a value greater than 40 μT
B)40 μT
C)a value less than 40 μT
D)It could be any value.

Question

Quizplus · Accepted Answer

The magnetic field midway between the conductors is given by
B = μ0I/2πd where μ0 is the permeability of free space, I is the current, and d is the distance between the conductors. When the currents are in opposite directions, the magnetic fields created by each cancel each other out at the midpoint, resulting in a net magnetic field of zero. When one current is reversed, the fields no longer perfectly cancel, but are still partially in opposite directions. This decreases the net magnetic field at the midpoint, resulting in a value less than 40 μT.

Two Parallel Conductors Are Carrying Currents in the Opposite Direction