The diagram illustrates a basic a.c. generator. A magnet turns about a stationary coil that is wound around a fixed iron core. The output electromotive force (e.m.f.) is a sine wave, made up of crests, zeros and troughs. The magnet is shown at three stages of its rotation, P, Q and R. At Q, the magnetic field in the coil is zero, but it is changing at the greatest rate. Which statement about the induced e.m.f. in the coil is correct?
- AThe magnitude of the e.m.f. at position Q is larger than that at position P.
- BThe magnitude of the e.m.f. at position Q is zero.
- CThe magnitude of the e.m.f. at position Q is smaller than that at position R, but not zero.
- DThe magnitude of the e.m.f. at position R is larger than that at position P.