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BASIC NEC 2023

Single-Phase Motor Types Practice Test

Free online single-phase motor types practice test. 25 basic electrical questions on split-phase, capacitor-start, PSC, and shaded-pole motors. Good for electrician exam prep.

TOPICS COVERED

Single-Phase Motor Basics Split-Phase Motors Motor Starting Mechanisms Capacitor-Start Motors PSC Motors Shaded-Pole Motors

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Unlike three-phase motors, single-phase motors are NOT self-starting on their own — they need a special mechanism to get the rotor turning before the main winding can keep it going. Different starting methods define the common motor types: split-phase, capacitor-start, permanent split-capacitor (PSC), and shaded-pole. Each type trades off starting torque, cost, and efficiency differently, which determines what application it is best suited for.

25

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38 min

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Single-Phase Motor Types Practice Test — Question List

Question 1: Why do single-phase induction motors generally need some type of starting mechanism to begin turning?

A single-phase winding alone produces a pulsating magnetic field, not a rotating one, so the rotor has no initial direction to start turning
Single-phase motors have no magnetic field at all
Single-phase motors are illegal to use in the US
Single-phase power cannot create any torque, ever

Question 2: A split-phase (resistance-start) motor creates its starting torque using:

A separate start winding with higher resistance than the run winding, creating a phase shift between the two windings' currents
A large external capacitor bank only
Three separate phase windings, like a 3-phase motor
A permanent magnet rotor with no windings at all

Question 3: The centrifugal switch in a split-phase or capacitor-start motor performs which function?

It disconnects the start winding once the motor reaches roughly 75% of its full running speed
It permanently disconnects power to the entire motor
It reverses the motor's direction of rotation
It has no real function and is purely decorative

Question 4: A capacitor-start motor uses a capacitor in series with the start winding mainly to:

Increase the phase shift between the run and start windings, producing significantly higher starting torque than a plain split-phase motor
Reduce the motor's starting torque to nearly zero
Eliminate the need for a run winding entirely
Convert the motor to run on three-phase power

Question 5: A capacitor-start capacitor-run (CSCR) motor is distinguished by having:

Two separate capacitors -- one for high starting torque, and a second smaller one that stays in the circuit continuously to improve running efficiency
No capacitors at all, unlike its name suggests
A start winding but no run winding
Only a permanent magnet rotor

Question 6: A permanent split-capacitor (PSC) motor uses a single run capacitor that:

Stays connected in the circuit continuously, both during starting and while running, with no centrifugal switch needed
Disconnects immediately after the motor starts, just like a capacitor-start motor
Is only used during motor shutdown
Has no effect on the motor whatsoever

Question 7: PSC motors are especially common in which type of application?

Fans and blowers, such as those used in HVAC condenser and furnace blower units
Heavy-duty compressors needing extremely high starting torque
Only large industrial cranes
Only elevator hoist motors

Question 8: A shaded-pole motor creates its starting torque using:

A small shorted copper "shading coil" on part of each pole, which delays the magnetic field in that section and creates a slight rotating effect
A large external run capacitor
A centrifugal switch and separate start winding
Three separate phase windings

Question 9: Among the common single-phase motor types, the shaded-pole motor is generally known for being the:

Simplest and lowest-cost design, but with the lowest starting torque
Most expensive and highest starting torque design
The only type that can run on three-phase power
The only type with no rotor at all

Question 10: Shaded-pole motors are most commonly found in which type of device?

Small fans and light-duty appliances, such as box fans and small exhaust fans
Heavy air compressors requiring high starting torque
Large industrial pumps only
Elevator drive motors only

Question 11: Of these single-phase motor types, which typically has the HIGHEST starting torque?

Capacitor-start
Shaded-pole
PSC (permanent split-capacitor)
They all have identical starting torque

Question 12: A refrigeration compressor needs a high-starting-torque motor because it must start while:

There is often residual pressure in the system working against the compressor, requiring extra force to get moving
Compressors have zero load and need no starting torque at all
Compressors only run on three-phase power
Compressors never need to start, they run continuously forever

Question 13: What is the key functional difference between a "start" capacitor and a "run" capacitor in a motor?

A start capacitor is only in the circuit briefly during startup, while a run capacitor stays connected continuously during normal operation
They are exactly the same component with no functional difference
A run capacitor is only used during startup
Neither type of capacitor is ever used in single-phase motors

Question 14: Split-phase (resistance-start) motors are typically used for loads that need:

Moderate starting torque, such as small pumps, fans, or washing machine drives
Only extremely heavy compressors needing maximum torque
No load at all, ever
Only three-phase industrial equipment

Question 15: If a centrifugal switch fails in the CLOSED (stuck) position on a split-phase motor, what problem is most likely to result?

The start winding stays energized continuously and can overheat/burn out, since it was only designed for brief use
The motor will run more efficiently than normal
Nothing changes, the switch has no real function
The motor will run in reverse permanently

Question 16: If a single-phase induction motor had ONLY a single run winding, with no start winding, capacitor, or shaded pole, what would generally happen if you tried to start it?

It would hum and vibrate but not turn on its own, needing a manual push to start spinning in a direction
It would start instantly with maximum torque
It would run in reverse automatically every time
It would run perfectly on three-phase power instead

Question 17: Because the run capacitor in a PSC motor stays in the circuit continuously, PSC motors generally have:

Better running efficiency and power factor than a plain split-phase motor
Worse running efficiency than any other motor type
No difference in efficiency compared to any other type
PSC motors cannot run continuously at all

Question 18: Because the shaded-pole design's rotation direction is fixed by the physical placement of the shading coils, these motors are typically:

Not easily reversible -- the direction of rotation is essentially fixed by construction
Always instantly reversible with a simple switch
Not motors at all, but purely resistive heating elements
Only usable on three-phase power systems

Question 19: Compared to a shaded-pole motor, a capacitor-start motor is generally:

More expensive and complex, but delivers much higher starting torque
Cheaper and simpler in every way
Exactly identical in cost, complexity, and torque
Impossible to manufacture

Question 20: Split-phase, capacitor-start, PSC, and shaded-pole motors are all considered types of:

Single-phase induction motors
Three-phase synchronous motors
DC series motors
Stepper motors only

Question 21: In a single-phase motor, the "run" winding (also called the main winding) is:

The primary winding that stays energized continuously and does most of the work while the motor is running normally
A winding used only during the first half-second of starting
A winding that only exists in three-phase motors
A winding with no electrical connection to the motor

Question 22: Compared to a PSC (permanent split-capacitor) motor, a CSCR (capacitor-start capacitor-run) motor generally offers:

Higher starting torque, thanks to the extra start capacitor used only during startup
Lower starting torque than a PSC motor
The exact same starting torque, with no difference at all
No starting torque whatsoever

Question 23: You are examining a single-phase motor and find it has a run capacitor but NO centrifugal switch anywhere inside. This is most consistent with which motor type?

PSC (permanent split-capacitor)
Split-phase (resistance-start)
Capacitor-start (single capacitor, disconnects at speed)
This combination is impossible in any motor

Question 24: Among common single-phase motor types, shaded-pole motors are generally known for having relatively:

Low overall efficiency, in addition to low starting torque
The highest efficiency of any single-phase motor type
100% efficiency with zero losses
No measurable efficiency at all

Question 25: You need to select a motor for a small decorative desk fan with a very light load and lowest possible cost. Which motor type is the best fit?

Shaded-pole
Capacitor-start (single-capacitor, high-torque design)
CSCR (capacitor-start capacitor-run)
A three-phase synchronous motor

EXAM CARD BASIC

Questions25

Time limit38 min

Pass score75%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

Timer starts immediately. Progress is auto-saved.

Source: NEC 2026 (NFPA 70)