CPM CPM - Certified Plant Mechanic Electrical Systems and Controls 1 — Questions and Answers
Question 1: What does NEC stand for in the context of US industrial electrical work?
- National Electrical Code (Correct answer)
- National Equipment Code
- Network Electrical Circuit
- Nominal Energy Capacity
Correct answer: National Electrical Code
NEC stands for National Electrical Code, the standard for safe installation of electrical wiring and equipment in the US.
Question 2: Which wire color designates a ground conductor in standard US wiring?
- White
- Black
- Green or bare copper (Correct answer)
- Red
Correct answer: Green or bare copper
Green or bare copper wire designates the equipment grounding conductor per NEC standards.
Question 3: What device protects a motor from damage caused by sustained overload currents?
- Circuit breaker
- Overload relay (Correct answer)
- Fuse
- Contactor
Correct answer: Overload relay
An overload relay monitors motor current and trips the starter circuit when current exceeds the setpoint for a defined time.
Question 4: What is the primary purpose of a GFCI outlet in an industrial plant environment?
- Regulate voltage fluctuations
- Protect against ground fault electric shock (Correct answer)
- Filter harmonic distortion
- Reduce power factor
Correct answer: Protect against ground fault electric shock
A GFCI (Ground Fault Circuit Interrupter) trips within milliseconds when it detects a difference between hot and neutral current, protecting personnel from shock.
Question 5: What condition results when a 3-phase motor loses one of its supply phases while running?
- Motor runs faster
- Motor reverses direction
- Single phasing occurs causing overheating (Correct answer)
- Motor enters standby mode
Correct answer: Single phasing occurs causing overheating
Single phasing causes the motor to draw excessive current on the remaining phases, leading to overheating and potential winding damage.
Question 6: What unit is used to measure electrical resistance in a circuit?
- Ampere
- Volt
- Watt
- Ohm (Correct answer)
Correct answer: Ohm
Electrical resistance is measured in ohms (Ω), as defined by Ohm's Law: V = I × R.
CPM CPM - Certified Plant Mechanic Electrical Systems and Controls 1
What does NEC stand for in the context of US industrial electrical work?