Question

Same current ''i'' is flowing in three infinitely long wire along positive x, y and z directions. The magnetic field-at a point (0,0-a) would be

• A. $\frac{\mu_0 i}{2\pi a}(\hat{j}-\hat{i})$
• B. $\frac{\mu_0 i}{2\pi a}(\hat{i}+\hat{j})$
• C. $\frac{\mu_0 i}{2\pi a}(\hat{i}-\hat{j})$
• D. $\frac{\mu_0 i}{2\pi a}(\hat{i}+\hat{j}+\hat{k})$

Answer 1

Answer: (A)

$\frac{\mu_0 i}{2\pi a}(\hat{j}-\hat{i})$

Answer 2

Magnetic field due to current along the z-axis is 0. and due to rest two wires is $\frac{\mu_0}{2\pi} \frac{i}{a}$ $B=\frac{\mu_0\,i}{2 \pi\,a}j$ $B_y=\frac{\mu_0\,i}{2 \pi\,a}(-\hat{i})$ $B_z=0$