NCCER Electrical Module 2 Level 2 Motors: Theory and
Application EXAM Questions & Answers Plus Rationales |
Latest Already Graded A+ UPDATE 2025|2026
1. Which part of a motor converts electrical energy into mechanical energy?
A. Commutator
B. Armature
C. Field coil
D. Rotor
✅ Correct Answer: D
Rationale: The rotor interacts with the magnetic field created by the stator to produce torque,
turning electrical energy into mechanical motion.
2. The stationary part of an AC motor that produces a rotating magnetic field is the:
A. Shaft
B. Stator
C. Winding spool
D. Commutator
✅ Correct Answer: B
Rationale: The stator contains coils arranged so that, when energized, they create a rotating
magnetic field that drives the rotor.
3. In a three-phase induction motor, how many electrical degrees separate each phase?
A. 60°
B. 90°
C. 120°
D. 180°
✅ Correct Answer: C
Rationale: Each phase in a three-phase system is displaced by 120° to create balanced torque
and smooth rotation.
4. The synchronous speed of a 4-pole motor on a 60 Hz supply is:
A. 900 RPM
B. 1,200 RPM
,C. 1,500 RPM
D. 1,800 RPM
✅ Correct Answer: D
Rationale: Synchronous
speed = (120 × frequency) ÷ number of poles → (120 × 60)/4 = 1,800 RPM.
5. Slip in an induction motor is defined as:
A. The ratio of torque to horsepower
B. The difference between synchronous and rotor speed
C. The speed of the magnetic field
D. The starting torque divided by full-load torque
✅ Correct Answer: B
Rationale: Slip measures how much slower the rotor rotates than the synchronous speed; it
allows induction of current in the rotor.
6. What type of single-phase motor uses a start capacitor and a run winding?
A. Shaded-pole motor
B. Split-phase capacitor-start motor
C. Repulsion motor
D. Universal motor
✅ Correct Answer: B
Rationale: The capacitor-start design provides high starting torque by phase-shifting the
auxiliary winding current.
7. Why are shaded-pole motors typically limited to small loads?
A. They draw excessive current
B. Their torque is low and efficiency poor
C. They require three-phase supply
D. They reverse automatically under load
✅ Correct Answer: B
Rationale: The simple shading coil design gives low starting torque, suitable only for small fans
and appliances.
8. To reverse the direction of rotation of a three-phase motor, you:
A. Swap any two supply leads
B. Adjust the overload relay
C. Rotate the stator
D. Replace the rotor
, ✅ Correct Answer: A
Rationale: Exchanging any two line connections (L1–L2, L2–L3, etc.) reverses the rotating
magnetic field and motor direction.
9. What causes inrush current when a motor first starts?
A. Low power factor
B. High rotor impedance
C. No back EMF at zero speed
D. Voltage unbalance
✅ Correct Answer: C
Rationale: At standstill the rotor produces no counter-electromotive force, so initial current is
limited only by winding resistance.
10. The full-load current (FLC) of a 5 HP, 230 V, single-phase motor is approximately:
A. 10 A
B. 20 A
C. 28 A
D. 40 A
✅ Correct Answer: C
Rationale: According to NEC Table 430.248, a 5 HP, 230 V, 1-phase motor draws about 28 A at
full load.
11. Which device is commonly used for motor overload protection?
A. Fuse
B. Magnetic contactor
C. Thermal overload relay
D. Selector switch
✅ Correct Answer: C
Rationale: A thermal overload relay senses heat buildup from excess current to protect the motor
windings from burnout.
12. The torque a motor produces while accelerating from standstill to rated speed is called:
A. Locked-rotor torque
B. Pull-up torque
C. Breakdown torque
D. Full-load torque
Application EXAM Questions & Answers Plus Rationales |
Latest Already Graded A+ UPDATE 2025|2026
1. Which part of a motor converts electrical energy into mechanical energy?
A. Commutator
B. Armature
C. Field coil
D. Rotor
✅ Correct Answer: D
Rationale: The rotor interacts with the magnetic field created by the stator to produce torque,
turning electrical energy into mechanical motion.
2. The stationary part of an AC motor that produces a rotating magnetic field is the:
A. Shaft
B. Stator
C. Winding spool
D. Commutator
✅ Correct Answer: B
Rationale: The stator contains coils arranged so that, when energized, they create a rotating
magnetic field that drives the rotor.
3. In a three-phase induction motor, how many electrical degrees separate each phase?
A. 60°
B. 90°
C. 120°
D. 180°
✅ Correct Answer: C
Rationale: Each phase in a three-phase system is displaced by 120° to create balanced torque
and smooth rotation.
4. The synchronous speed of a 4-pole motor on a 60 Hz supply is:
A. 900 RPM
B. 1,200 RPM
,C. 1,500 RPM
D. 1,800 RPM
✅ Correct Answer: D
Rationale: Synchronous
speed = (120 × frequency) ÷ number of poles → (120 × 60)/4 = 1,800 RPM.
5. Slip in an induction motor is defined as:
A. The ratio of torque to horsepower
B. The difference between synchronous and rotor speed
C. The speed of the magnetic field
D. The starting torque divided by full-load torque
✅ Correct Answer: B
Rationale: Slip measures how much slower the rotor rotates than the synchronous speed; it
allows induction of current in the rotor.
6. What type of single-phase motor uses a start capacitor and a run winding?
A. Shaded-pole motor
B. Split-phase capacitor-start motor
C. Repulsion motor
D. Universal motor
✅ Correct Answer: B
Rationale: The capacitor-start design provides high starting torque by phase-shifting the
auxiliary winding current.
7. Why are shaded-pole motors typically limited to small loads?
A. They draw excessive current
B. Their torque is low and efficiency poor
C. They require three-phase supply
D. They reverse automatically under load
✅ Correct Answer: B
Rationale: The simple shading coil design gives low starting torque, suitable only for small fans
and appliances.
8. To reverse the direction of rotation of a three-phase motor, you:
A. Swap any two supply leads
B. Adjust the overload relay
C. Rotate the stator
D. Replace the rotor
, ✅ Correct Answer: A
Rationale: Exchanging any two line connections (L1–L2, L2–L3, etc.) reverses the rotating
magnetic field and motor direction.
9. What causes inrush current when a motor first starts?
A. Low power factor
B. High rotor impedance
C. No back EMF at zero speed
D. Voltage unbalance
✅ Correct Answer: C
Rationale: At standstill the rotor produces no counter-electromotive force, so initial current is
limited only by winding resistance.
10. The full-load current (FLC) of a 5 HP, 230 V, single-phase motor is approximately:
A. 10 A
B. 20 A
C. 28 A
D. 40 A
✅ Correct Answer: C
Rationale: According to NEC Table 430.248, a 5 HP, 230 V, 1-phase motor draws about 28 A at
full load.
11. Which device is commonly used for motor overload protection?
A. Fuse
B. Magnetic contactor
C. Thermal overload relay
D. Selector switch
✅ Correct Answer: C
Rationale: A thermal overload relay senses heat buildup from excess current to protect the motor
windings from burnout.
12. The torque a motor produces while accelerating from standstill to rated speed is called:
A. Locked-rotor torque
B. Pull-up torque
C. Breakdown torque
D. Full-load torque
