Question

Two parallel conductors are carrying currents in the same 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?

Answer 1

Answer:

The magnitude of magnetic field decreases in comparison to previous case.

Explanation:

Let current flowing  in two conductors  are $I_1$ and $I_2$

Magnetic field in wire,$B=\frac{\mu_0 I}{2\pi r}$

Magnetic field due to current I1

$B_1=\frac{\mu_0 I_1}{2\pi r}$

Magnetic field due to current I2

$B_2=\frac{\mu_0 I}{2\pi r}$

When two parallel conductors are carrying currents in the same direction  then the magnetic field will be added.

$B=B_1+B_2=40\mu T$

When the  direction of one of the current is reversed  then  the magnitude of the  magnetic field midway between them

$B=B_1-B_2=\frac{\mu_0I_1}{2\pi r}-\frac{\mu_0 I_2}{2\pi r}$

$B=\frac{\mu_0(I_1-I_2)}{2\pi r}$

Hence, the magnitude of magnetic field decreases in comparison to previous case.