The figure shows three indentical current carryng square loops `A, B` and `C`. Identify the correct statement related to magnetic field B at the centre `O` of the square loop. Current in each wire is I.

Options

A. `vecB` is zero in all cases
B. `vecB` is zero only in case of C
C. `vecB` is non zero in all cases
D. `vecB` is non zero only in case of B

Answer

B

Explanation

In (c), two wires are producing `square` magnetic field and two wires are producing `ox` magnetic field.