Starting Systems Questions and Answers

Answer: A

A series motor develops very high torque at stall, which is exactly what an engine needs to be turned from rest. Its speed rises without limit off load, which does not matter because the pinion disengages. Compound machines are used in some heavy duty starters. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Naming what changes and what stays the same is the reliable route through questions of this shape.

Answer: B

Field current and armature current are the same, so torque rises with the square of the current and is greatest when stalled. Efficiency is actually poor, which is acceptable for a duty lasting a few seconds. The torque characteristic is what matters. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb.

Answer: C

With no load the field weakens as the current falls and the speed rises without limit, which can burst the armature. In a starter the pinion disengages before that can happen. It is why a series motor is never bench run uncoupled at full voltage. Naming what changes and what stays the same is the reliable route through questions of this shape. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.

Answer: D

The solenoid pulls a plunger that moves a lever, sliding the drive assembly along the shaft into mesh before closing the main contacts. Inertia starters did use the armature rotation to throw the pinion into mesh, which makes the alternatives historically real. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. The order in which the effects act is what decides the outcome, so it is worth establishing first.

Answer: A

Engaging before applying full power avoids clashing teeth and is precisely what pre-engaged means. The last option describes the older inertia type, which engaged by rotation and was noisy and destructive by comparison. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Most errors here come from carrying a result across from a neighbouring case where it does not hold.

Answer: B

A Bendix pinion is carried on a coarse screw thread and its inertia throws it along into mesh when the armature spins. It is simple but noisy and hard on the ring gear. Pre-engaged drives superseded it. The order in which the effects act is what decides the outcome, so it is worth establishing first. The shared behaviour explains why these belong together and the differences explain why both exist. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: C

A roller or sprag clutch transmits torque from motor to engine but freewheels the other way. Without it a firing engine would spin the armature to destruction before the driver released the key. The solenoid does release, but not instantly. Checking which component actually carries the load settles most questions of this kind at once. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: D

A slipping clutch lets the armature spin freely with the pinion engaged, so the motor whirs and nothing turns. A seized clutch would produce the overspeed, which makes the second option the opposite failure of the same part. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Working one numerical case through both cases side by side fixes the distinction better than any rule of thumb.

Answer: A

The solenoid is both an actuator and a relay, engaging the drive and then closing contacts that carry two hundred amps or more. Separating the two duties would need an extra component. That dual role is why it has two windings. The shared behaviour explains why these belong together and the differences explain why both exist. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: B

The pull-in winding is heavy and is short circuited once the contacts close, leaving the lighter hold-on winding to keep the plunger home. That arrangement gives a strong pull without a continuous heavy current. Primary and secondary belong to an ignition coil. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Naming what changes and what stays the same is the reliable route through questions of this shape.