Question

Four very long wires are arranged as shown, so that their cross-section forms a square, with connections at the ends so that current I flows through all four wires as shown. Length of each side of the formed such square is b. The magnetic field at the central point P (centre of the square) is

• A. $\frac{\mu_0 I}{\pi b}$
• B. $\frac{2 \mu_0 I}{\pi b}$
• C. 0
• D. $\frac{\mu_0 I}{ \sqrt{2} \pi b}$

Answer 1

Answer: (C)

0

Answer 2

Since, the current through two wires are from left to right, the magnetic field is directed outwards the plane of the paper. Also, current through the other two wires are from right to left, the magnetic field due to them is directed inwards the plane of the paper. Since, the value of current through all the wires is same and point $P$ is equidistant from all the wires, the magnitude of magnetic fields are same. Hence, they are cancelled. So, the net magnetic field is zero.