Which of the following is NOT a component of an a.c. generator?

Analyze the question: We need the part that does NOT belong in an a.c. generator (alternator).

Concept: An a.c. generator converts mechanical energy into alternating current using electromagnetic induction. Its main parts are:

• Magnet (or field magnet): produces the magnetic field.
• Armature: the coil that rotates in the field, so an e.m.f. is induced in it.
• Slip rings: two continuous rings, each joined to one end of the coil. They let the current keep alternating in direction as the coil rotates.
• Carbon brushes: press against the slip rings and carry current to the external circuit.

Comparison with a d.c. generator: A d.c. generator uses a split-ring commutator. The split rings reverse the connections every half turn, so the output in the external circuit flows in one direction only.

Going through the options:

• A. Armature: present in an a.c. generator.
• B. Carbon brushes: present.
• C. Magnet: present.
• D. Slip ring: present.
• E. Split rings: this belongs to the d.c. generator, not the a.c. generator.

Answer: E, Split rings.

Tip: Remember "Slip = Streaming alternating current (a.c.)" and "Split = Single direction (d.c.)". If you see slip rings, think a.c. If you see split rings (commutator), think d.c.