A semicircular wire of radius R is rotated with constant angular velocity about an axis passing through one end and perpendicular to the plane of the wire. There is a uniform magnetic field of strength B. The induced emf between the ends is

We connect a conducting wire from A to C and complete the semicircular loop.The emf in the semicircular loop iszero be cause its magnetic flux does not change.∴ emf of section APC + emf of  section CQA = 0∴ emf of section APC = emf of section AQC=2BR2ω