Calculate the magnitude of the magnetic field at point P as shown in Fig, in terms of `R,I_1 and I_2`.

Explanation

There is no contribution from the straight wires, and now we have
two oppositely oriented contributions from the two semicircles
`B=(B_1-B_2)=1/2((mu_0)/(2R))|I_1-I_2|`,
into the page. Note that if the two currents are equal, the magnetic
field goes to zero at the centre of the loop.