Question: What is the magnitude of the average emf induced in the coil?
A coil has N turns enclosing an area of A. In a physics laboratory experiment, the coil is rotated during the time interval Δt from a position in which the plane of each turn is perpendicular to Earth's magnetic field to one in which the plane of each turn is parallel to the field. The magnitude of Earth's magnetic field at the lab location is B.
If a symbolic answer is required, your expression must include B, A, and any other variables.