Two identical circular wires P and Q, each of radius R and carrying current I, are kept in perpendicular planes such that they have a common centre as shown in the figure. Find the magnitude and direction of the net magnetic field at the common centre of the two coils.

The magnetic field would be in the direction perpendicular to the plane of the coil for which the magnetic field is calculated. Hence, the magnetic field due to each coil is μ₀I/(2R), perpendicular to each other. Hence, the magnitude of the resultant field is √2 μ₀I/(2R). The net field would be inclined equally to both the fields.