Charging Systems and Alternators Questions and Answers

Answer: A

A commutator belongs to a direct current machine, where it reverses the coil current; an alternator uses slip rings instead. Rotor, stator and rectifier are all alternator parts. That distinction separates the alternator from the dynamo it replaced. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. The shared behaviour explains why these belong together and the differences explain why both exist.

Answer: B

Weakening or strengthening the magnetic field is the only control available, and it is enough to hold the voltage steady across the whole speed and load range. Modern regulators switch the field transistor rapidly and vary the duty cycle. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: C

Slip rings feed the rotor, the claw poles shape the field into alternating north and south poles, and the field diodes take over the supply once the machine self excites. Together they explain how excitation works. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Reading the definition literally, rather than recalling a summary, avoids the usual confusion.

Answer: D

One coil between two claw shaped pole pieces produces twelve or sixteen alternating poles with a single winding. Distributed windings genuinely are used in industrial machines and in some high output alternators, which makes the last option real. Naming what changes and what stays the same is the reliable route through questions of this shape. Most errors here come from carrying across a result from a neighbouring case where it does not hold.

Answer: A

Output frequency is pole pairs times revolutions per second, so it varies widely with engine speed. That is precisely why rectification is needed rather than direct use. Some engine controllers read that frequency to sense alternator speed. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Naming what changes and what stays the same is the reliable route through questions of this shape.