In an alternating current generator, the emf induced in the rotating coil is maximum when the plane of the coil is
- A. perpendicular to the magnetic field
- B. parallel to the magnetic field
- C. at 45 degrees to the field
- D. irrelevant, since the emf is constant
Explanation
The emf depends on the rate of change of flux, not on the flux itself, and that rate is greatest when the coil is edge on to the field, precisely where the flux through it is momentarily zero. When the plane is perpendicular to the field the flux is maximum but is instantaneously stationary, so the emf is zero. This quarter cycle offset between flux and emf is what makes the output sinusoidal.
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