CPT Electrical & Mechanical Fundamentals 3 — Questions and Answers
Question 1: Which lubrication method delivers a metered, continuous supply of oil to bearings during machine operation?
- Splash lubrication
- Centralized oil mist system (Correct answer)
- Grease packing
- Manual oiling with an oil can
Correct answer: Centralized oil mist system
A centralized oil mist system atomizes oil and delivers it continuously through distribution lines to multiple bearing points simultaneously.
Question 2: What electrical safety device automatically opens a circuit when current exceeds a predetermined level and must be manually reset?
- Fuse
- Ground fault circuit interrupter (GFCI)
- Circuit breaker (Correct answer)
- Surge protector
Correct answer: Circuit breaker
A circuit breaker trips (opens) on overcurrent and can be manually reset after the fault is cleared, unlike a fuse which must be replaced.
Question 3: In mechanical power transmission, what is 'backlash' in a gear set?
- The gear tooth surface hardness
- The clearance between mating gear teeth (Correct answer)
- The speed ratio between driver and driven gears
- The amount of gear tooth wear over time
Correct answer: The clearance between mating gear teeth
Backlash is the play or clearance between meshing gear teeth, necessary to allow for lubrication and thermal expansion but excessive backlash causes noise and inaccuracy.
Question 4: A three-phase motor has its rotation reversed by:
- Reversing the polarity of the ground wire
- Swapping any two of the three power leads (Correct answer)
- Increasing the supply voltage by 10%
- Disconnecting the neutral wire
Correct answer: Swapping any two of the three power leads
Swapping any two of the three phase conductors reverses the phase sequence, which reverses the direction of the motor's rotating magnetic field and shaft rotation.
Question 5: What is the function of a pneumatic FRL unit (Filter-Regulator-Lubricator) in a compressed air system?
- Generate and store compressed air
- Condition air by removing moisture/contaminants, regulating pressure, and adding lubrication (Correct answer)
- Convert air pressure to electrical signals
- Control the direction of airflow to actuators
Correct answer: Condition air by removing moisture/contaminants, regulating pressure, and adding lubrication
An FRL unit conditions compressed air by filtering out particles and moisture, regulating pressure to the required level, and adding a fine oil mist for tool/actuator lubrication.
Question 6: What type of coupling is used to connect two shafts that may have slight angular or parallel misalignment?
- Rigid flange coupling
- Flexible jaw coupling (Correct answer)
- Solid sleeve coupling
- Keyed bushing
Correct answer: Flexible jaw coupling
Flexible jaw (spider) couplings accommodate minor angular and parallel misalignment through a resilient elastomeric insert, reducing vibration transmission.
Question 7: Which electrical wiring color is designated as the equipment grounding conductor in US NEC standards?
- White or gray
- Black
- Red
- Green or bare copper (Correct answer)
Correct answer: Green or bare copper
Per the NEC, green insulation or bare copper wire designates the equipment grounding conductor (EGC) which provides a fault current return path to protect personnel.
CPT Electrical & Mechanical Fundamentals 3
Which lubrication method delivers a metered, continuous supply of oil to bearings during machine operation?