A current loop, having two circular arcs joined by two radial lines as shown in the figure. It carries a current of 10 A. The magnetic field at point O will be close to

From the given figure as shown belowThe magnetic field at point O due to wires PQ and RS will be zero.Magnetic field due to arc QR at point O will be          B1=θ2πμ0i2aHere, θ=45∘=π4rad,i=10Aand a=3cm=3×10−2m⇒ B1=π2π×4μ0×102×3×10−2=μ0×52×12×10−2=5×μ0×10224Direction of field B1 will be coming out of the plane of figure.Similarly, field at point O due to arc SP will beB2=π412πμ0×102×(2+3)×10−2=μ0×1028Direction of B2 is going into the plane of the figure.∴The resultant field at O isB=B1−B2=125×μ012×10−2−μ04×10−2                    =4π×10−712×10−2≅1×10−5T