Question

Five long wires A, B, C, D and E, each carrying current I are arranged to form edges of a pentagonal prism as shown in figure. Each carries current out of the plane of paper. Axis is at a distance R from each wire.
What will be magnetic induction at a point on the axis O?

Answer 1

Given, current carried by each wire = I
If n co-planar vectors are situated at an equal angle from each other, their vector sum will be zero at their centre.
As point O on the axis is equidistant from all the wires and all the wires are in same plane, and each carries current out of the plane of paper. So, net magnetic field $B_{net}$ will be zero.

Final Answer: zero