Mechanics Exam NEIEP (2024/2025) –
Questions with Verified Correct Answers
(Updated Version)
Section 1: Waveforms and Electrical Theory (12 Qs)
1. In AC electrical theory, what is the primary cause of waveform distortion in an elevator's
three-phase supply?
A) Harmonic interference from VFD drives
B) DC motor back-EMF
C) Resistive load imbalance
D) Capacitive coupling
Answer: A
Rationale: Variable Frequency Drives (VFDs) introduce harmonics (e.g., 5th/7th order),
distorting sinusoidal waveforms and causing overheating in motors. Per NEIEP Semester 300,
monitor THD <5% to comply with IEEE 519 standards.
2. A sine wave in an elevator controller has a peak voltage of 170V. What is the RMS value?
A) 120V
B) 170V
C) 240V
D) 340V
Answer: A
Rationale: RMS = Peak / √2 ≈ .414 = 120V. Essential for calculating power in AC circuits
(P = V_RMS × I_RMS × PF), as covered in NEIEP electrical theory modules.
3. In a Ward-Leonard system, the generator waveform shows excessive ripple. Likely cause?
A) Faulty commutator brushes
B) Overloaded armature
C) Incorrect field excitation
D) Loose sheave
Answer: A
Rationale: Worn brushes cause arcing, introducing ripple in DC output waveform. NEIEP
troubleshooting requires brush replacement and gap adjustment to 0.015-0.025 inches.
, 4. What unit measures the rate of change in an AC waveform's voltage?
A) Hertz (frequency)
B) Volt-seconds (flux)
C) Amperes (current)
D) Ohms (impedance)
Answer: A
Rationale: Hertz measures cycles per second, determining waveform frequency (e.g., 60 Hz
standard). Critical for synchronizing elevator motor drives per NEIEP 400.
Section 2: Force, Motion, and Resistance Calculation (12 Qs)
11. An elevator car (mass 1500 kg) accelerates upward at 1.5 m/s². What is the tension in the
hoisting cable (g=9.8 m/s²)?
A) 14,700 N
B) 17,520 N
C) 20,340 N
D) 23,160 N
Answer: B
Rationale: T - mg = ma → T = m(g + a) = 1500(9.8 + 1.5) = 17,520 N. NEIEP mechanics
emphasize Newton's 2nd Law for traction systems; counterweight reduces effective load.
12. A hydraulic elevator pump delivers 400 PSI working pressure. What is the maximum relief
valve setting?
A) 400 PSI
B) 500 PSI
C) 600 PSI
D) 800 PSI
Answer: C
Rationale: Max = 1.5 × working pressure = 600 PSI (ASME A17.1). Prevents pump damage
during overload; NEIEP hydro troubleshooting requires annual calibration.
13. Friction resistance in guide rails is 500 N. Car mass 1000 kg, velocity 100 fpm constant. Net
force?
A) 0 N
B) 500 N
C) 9,800 N
D) 10,300 N
Answer: A
Rationale: Constant velocity → net force = 0 (friction balanced by drive force). NEIEP motion
calcs use F_net = ma; adjust lubrication to minimize rail friction (<2% of weight).
Questions with Verified Correct Answers
(Updated Version)
Section 1: Waveforms and Electrical Theory (12 Qs)
1. In AC electrical theory, what is the primary cause of waveform distortion in an elevator's
three-phase supply?
A) Harmonic interference from VFD drives
B) DC motor back-EMF
C) Resistive load imbalance
D) Capacitive coupling
Answer: A
Rationale: Variable Frequency Drives (VFDs) introduce harmonics (e.g., 5th/7th order),
distorting sinusoidal waveforms and causing overheating in motors. Per NEIEP Semester 300,
monitor THD <5% to comply with IEEE 519 standards.
2. A sine wave in an elevator controller has a peak voltage of 170V. What is the RMS value?
A) 120V
B) 170V
C) 240V
D) 340V
Answer: A
Rationale: RMS = Peak / √2 ≈ .414 = 120V. Essential for calculating power in AC circuits
(P = V_RMS × I_RMS × PF), as covered in NEIEP electrical theory modules.
3. In a Ward-Leonard system, the generator waveform shows excessive ripple. Likely cause?
A) Faulty commutator brushes
B) Overloaded armature
C) Incorrect field excitation
D) Loose sheave
Answer: A
Rationale: Worn brushes cause arcing, introducing ripple in DC output waveform. NEIEP
troubleshooting requires brush replacement and gap adjustment to 0.015-0.025 inches.
, 4. What unit measures the rate of change in an AC waveform's voltage?
A) Hertz (frequency)
B) Volt-seconds (flux)
C) Amperes (current)
D) Ohms (impedance)
Answer: A
Rationale: Hertz measures cycles per second, determining waveform frequency (e.g., 60 Hz
standard). Critical for synchronizing elevator motor drives per NEIEP 400.
Section 2: Force, Motion, and Resistance Calculation (12 Qs)
11. An elevator car (mass 1500 kg) accelerates upward at 1.5 m/s². What is the tension in the
hoisting cable (g=9.8 m/s²)?
A) 14,700 N
B) 17,520 N
C) 20,340 N
D) 23,160 N
Answer: B
Rationale: T - mg = ma → T = m(g + a) = 1500(9.8 + 1.5) = 17,520 N. NEIEP mechanics
emphasize Newton's 2nd Law for traction systems; counterweight reduces effective load.
12. A hydraulic elevator pump delivers 400 PSI working pressure. What is the maximum relief
valve setting?
A) 400 PSI
B) 500 PSI
C) 600 PSI
D) 800 PSI
Answer: C
Rationale: Max = 1.5 × working pressure = 600 PSI (ASME A17.1). Prevents pump damage
during overload; NEIEP hydro troubleshooting requires annual calibration.
13. Friction resistance in guide rails is 500 N. Car mass 1000 kg, velocity 100 fpm constant. Net
force?
A) 0 N
B) 500 N
C) 9,800 N
D) 10,300 N
Answer: A
Rationale: Constant velocity → net force = 0 (friction balanced by drive force). NEIEP motion
calcs use F_net = ma; adjust lubrication to minimize rail friction (<2% of weight).
