Ohio Maintenance Technician Exam: Actual Multiple-
Choice Questions with Answers & Explanations |
Instant Pdf Download
1–20: Electrical Systems & Safety
1. A circuit has a resistance of 24 Ω and an applied voltage of 120 V. What is the current?
A) 2 A
B) 5 A
C) 10 A
D) 2880 A
B) 5 A ✓ Ohm’s Law: I = V ÷ R = 120 ÷ 24 = 5 A.
2. Which NEC table is used to determine the ampacity of copper conductors in a raceway or
cable?
A) Table 310.16
B) Table 430.52
C) Table 250.66
D) Table 220.42
A) Table 310.16 ✓ NEC Table 310.16 gives allowable ampacities for insulated conductors
rated up to 2000 V.
,3. A three-phase induction motor runs at 1750 RPM on a 60 Hz supply. How many poles
does it have?
A) 2
B) 4
C) 6
D) 8
B) 4 ✓ Synchronous speed = 120 × f ÷ P. For 4 poles: 120 × 60 ÷ 4 = 1800 RPM; slip gives
1750 RPM.
4. What device provides the principal means of disconnecting power to an entire industrial
control panel?
A) Contactor
B) Overload relay
C) Fused disconnect switch
D) Pushbutton station
C) Fused disconnect switch ✓ The main disconnect must open all ungrounded supply
conductors and be clearly marked.
5. A digital multimeter is set to read AC voltage. What type of waveform does it typically
display a value for?
A) Peak-to-peak
,B) Peak
C) Average
D) RMS
D) RMS ✓ Most DMMs display the root-mean-square value for AC, which equates to
effective heating value.
6. A fuse marked “FRN-R-20” is what type?
A) Fast-acting 20 A, 250 V
B) Dual-element time-delay 20 A, 250 V
C) Class J 20 A
D) High-speed semiconductor fuse
B) Dual-element time-delay 20 A, 250 V ✓ “FRN-R” is a Fusetron dual-element fuse for
motor circuits (time-delay).
7. Which color is the equipment-grounding conductor in a typical 120 V branch circuit?
A) White
B) Black
C) Green or bare
D) Red
C) Green or bare ✓ NEC requires equipment-grounding conductors to be green, green
with yellow stripe, or bare.
, 8. A relay that uses a bimetallic strip to open contacts on overload is called a:
A) Contactor
B) Thermal overload relay
C) Mercury relay
D) Reed relay
B) Thermal overload relay ✓ Thermal overloads rely on heat from motor current bending a
bimetallic element to trip.
9. A VFD controls motor speed by varying:
A) Voltage only
B) Number of poles
C) Frequency and voltage
D) Slip rings
C) Frequency and voltage ✓ Variable Frequency Drives maintain the V/Hz ratio to control
speed and torque.
10. Lockout/tagout is required by OSHA under which standard?
A) 1910.120
B) 1910.147
C) 1926.451
D) 1910.333
Choice Questions with Answers & Explanations |
Instant Pdf Download
1–20: Electrical Systems & Safety
1. A circuit has a resistance of 24 Ω and an applied voltage of 120 V. What is the current?
A) 2 A
B) 5 A
C) 10 A
D) 2880 A
B) 5 A ✓ Ohm’s Law: I = V ÷ R = 120 ÷ 24 = 5 A.
2. Which NEC table is used to determine the ampacity of copper conductors in a raceway or
cable?
A) Table 310.16
B) Table 430.52
C) Table 250.66
D) Table 220.42
A) Table 310.16 ✓ NEC Table 310.16 gives allowable ampacities for insulated conductors
rated up to 2000 V.
,3. A three-phase induction motor runs at 1750 RPM on a 60 Hz supply. How many poles
does it have?
A) 2
B) 4
C) 6
D) 8
B) 4 ✓ Synchronous speed = 120 × f ÷ P. For 4 poles: 120 × 60 ÷ 4 = 1800 RPM; slip gives
1750 RPM.
4. What device provides the principal means of disconnecting power to an entire industrial
control panel?
A) Contactor
B) Overload relay
C) Fused disconnect switch
D) Pushbutton station
C) Fused disconnect switch ✓ The main disconnect must open all ungrounded supply
conductors and be clearly marked.
5. A digital multimeter is set to read AC voltage. What type of waveform does it typically
display a value for?
A) Peak-to-peak
,B) Peak
C) Average
D) RMS
D) RMS ✓ Most DMMs display the root-mean-square value for AC, which equates to
effective heating value.
6. A fuse marked “FRN-R-20” is what type?
A) Fast-acting 20 A, 250 V
B) Dual-element time-delay 20 A, 250 V
C) Class J 20 A
D) High-speed semiconductor fuse
B) Dual-element time-delay 20 A, 250 V ✓ “FRN-R” is a Fusetron dual-element fuse for
motor circuits (time-delay).
7. Which color is the equipment-grounding conductor in a typical 120 V branch circuit?
A) White
B) Black
C) Green or bare
D) Red
C) Green or bare ✓ NEC requires equipment-grounding conductors to be green, green
with yellow stripe, or bare.
, 8. A relay that uses a bimetallic strip to open contacts on overload is called a:
A) Contactor
B) Thermal overload relay
C) Mercury relay
D) Reed relay
B) Thermal overload relay ✓ Thermal overloads rely on heat from motor current bending a
bimetallic element to trip.
9. A VFD controls motor speed by varying:
A) Voltage only
B) Number of poles
C) Frequency and voltage
D) Slip rings
C) Frequency and voltage ✓ Variable Frequency Drives maintain the V/Hz ratio to control
speed and torque.
10. Lockout/tagout is required by OSHA under which standard?
A) 1910.120
B) 1910.147
C) 1926.451
D) 1910.333
