Question

Four infinity long 'L' shaped wires, each carrying a current I have been arranged as shown in the figure. Obtain the magnetic field strength at the point 'O' equidistant from all the four corners.

Answer 1

We know that,

$B=\frac{{\mu }_{o}I}{4\pi a}(\sin {\theta }_2+\sin {\theta }_1)$

The net magnetic field due to wires from left to night and from right to left is zero as they cancel out. By applying the right-hand thumb rule. As the left sides, the magnetic field adds up & direction is upward whereas the right-side magnetic field adds up to but direction is downward. So, cancels up.

And for the wires from up to down or down to up, it is the wires cancel its conjugate according to right-hand thumb-rule.

Thus, net magnetic field at a point is $0$.