Plant Operator Selection System Test Plant Operator Selection System Physics Principles 5 — Questions and Answers
Question 1: In a series electrical circuit, if one component fails open (breaks), what happens to current flow?
- Current increases in the remaining components
- Current decreases but still flows
- Current stops completely throughout the circuit (Correct answer)
- Only the failed component loses current
Correct answer: Current stops completely throughout the circuit
In a series circuit there is only one path for current; an open break stops all current flow in the entire loop.
Question 2: A flywheel is used on a reciprocating engine primarily to:
- Increase the compression ratio
- Store rotational energy and smooth out power pulses (Correct answer)
- Reduce lubricating oil consumption
- Control valve timing
Correct answer: Store rotational energy and smooth out power pulses
Flywheels store kinetic energy during power strokes and release it during non-power strokes, smoothing rotational speed.
Question 3: Which condition causes cavitation in a centrifugal pump?
- Excessive discharge pressure
- Suction pressure falling below the fluid's vapor pressure (Correct answer)
- Overlubrication of bearings
- Running at below-rated amperage
Correct answer: Suction pressure falling below the fluid's vapor pressure
Cavitation occurs when local pressure drops below vapor pressure, forming vapor bubbles that collapse and damage impeller surfaces.
Question 4: Work is defined as:
- Force multiplied by time
- Force multiplied by distance in the direction of the force (Correct answer)
- Mass multiplied by acceleration
- Energy divided by power
Correct answer: Force multiplied by distance in the direction of the force
Work (W) = Force (F) × Distance (d) in the direction the force acts; applying force without movement does no work.
Question 5: Which type of valve is best suited for fully open or fully closed service and NOT for flow throttling?
- Globe valve
- Needle valve
- Gate valve (Correct answer)
- Ball valve with a V-port
Correct answer: Gate valve
Gate valves are designed for on/off isolation; partial opening causes erosion, vibration, and poor flow control.
Question 6: Heat flows from a hotter object to a cooler object until:
- The hotter object runs out of heat energy
- Thermal equilibrium is reached between the two objects (Correct answer)
- The cooler object reaches 32°F
- All kinetic energy is converted to potential energy
Correct answer: Thermal equilibrium is reached between the two objects
The Second Law of Thermodynamics states heat naturally flows from high temperature to low temperature until both objects reach the same temperature.
Question 7: An operator notices a vibrating pipe resonating at a certain frequency. The most effective fix is to:
- Increase fluid velocity to push past resonance
- Add a support or change the pipe span to shift its natural frequency (Correct answer)
- Reduce pipe wall thickness to absorb vibration
- Increase operating pressure to stiffen the pipe
Correct answer: Add a support or change the pipe span to shift its natural frequency
Adding supports or changing span length alters the pipe's natural frequency so it no longer matches the excitation frequency and resonance stops.
Plant Operator Selection System Test Plant Operator Selection System Physics Principles 5
In a series electrical circuit, if one component fails open (breaks), what happens to current flow?