Two thick wires and two thin wires, all of same material and same length from a square in three different ways P,Q and R as shown in the figure. With correct connections shown, the magnetic field due to the current flow at the centre of the loop will be zero in case of

Options

A. Q and R only
B. p only
C. P and Q only
D. P and R only

Answer

D

Explanation

In P and R only, as current divides equally in the two halves because of equal resistance in the two halves. The current in the two halves thgan make the firld at centre zero.