Answer / meenakshi

The rotor of alternator consists of a coil of wire wrapped
around an iron core. Current through the wire coil -
called "field" current - produces a magnetic field around
the core. The strength of the field current determines the
strength of the magnetic field. The field current is D/C,
or direct current so that the current flows in one
direction only, and is supplied to the wire coil

Answer / rps

because we need constant magnetic flux so that windings of armature can cut them & induce emf.

Answer / k.prakashchandra

Field requires poles of alternative(N &S) fixed
polarities,which is possible only with DC

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