A long straight conductor is bent into shape as shown. If it carries 1 ~A and its radius is R , then magnetic ficld B at the centre of circular coil

Step-by-step solution

Magnetic field at centre O= magnetic field due to reaction A B+ magnetic field due to section P Q R B₀=B_ A B +B_ P Q R but B_ A B = ₀ i 2 R (upside the plane of paper) and B_ P Q R = ₀ i 2 R (inside the plane of paper) Hence B₀= ₀ i 2 R - ₀ i 2 R B₀= ₀ i( -1) 2 R