Engineer Examination Practice Questions And

Coast Guard QMED Electrician/Refrigerating Engineer Examination Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the purpose of a circuit breaker in an electrical system?
• Increase voltage
• Store electrical energy
• Interrupt current during a fault
• Convert AC to DC

Rationale: A circuit breaker protects the system by automatically

interrupting current when a fault occurs, preventing damage and fire hazards.

• Which type of refrigerant is commonly used in marine refrigeration

systems?

• Ammonia
• Carbon dioxide
• R-134a 1 / 4

• Propane

Rationale: R-134a is widely used in marine refrigeration due to its non-

toxic, non-flammable properties and compatibility with system components.

• What does Ohm’s Law state?
• Power = Current × Voltage
• Voltage = Current × Resistance
• Resistance = Voltage × Power
• Current = Power × Resistance

Rationale: Ohm’s Law defines the relationship between voltage, current,

and resistance: V = I × R.

• In a three-phase AC system, what is the phase angle difference between

phases?

A. 30°

B. 60°

C. 120°

D. 180°

Rationale: Three-phase AC systems have phases spaced 120° apart to

maintain balanced power distribution.

• What is the function of a starter in an electric motor?
• Increase motor speed
• Decrease current
• Limit inrush current during startup 2 / 4

• Reverse motor rotation

Rationale: Starters limit the high inrush current when starting a motor,

protecting it from damage.

• Which tool is used to measure insulation resistance?
• Voltmeter
• Ammeter
• Megohmmeter
• Ohmmeter

Rationale: A megohmmeter measures high resistance in insulation to check

its integrity.

• How is AC voltage generated in a generator?
• By applying a battery to a coil
• By using a transformer
• By rotating a coil in a magnetic field
• By electrolysis

Rationale: AC voltage is produced by rotating a coil within a magnetic

field, inducing alternating current.

• What is the primary purpose of a condenser in a refrigeration system?
• Reduce pressure in the system
• Remove heat from the refrigerant
• Compress refrigerant vapor
• Absorb heat from the cargo space 3 / 4

Rationale: The condenser dissipates heat from the refrigerant, turning it

from vapor to liquid.

• Which device protects motors from overheating?
• Circuit breaker
• Voltmeter
• Thermal overload relay
• Transformer

Rationale: Thermal overload relays disconnect the motor if current exceeds

safe levels for a prolonged period, preventing overheating.

• What is the unit of electrical power?
• Ohm
• Volt
• Watt
• Ampere

Rationale: Electrical power is measured in watts, representing the rate of

energy transfer.

• Which component is used to increase or decrease AC voltage?
• Rectifier
• Motor
• Transformer
• Capacitor

Rationale: Transformers adjust AC voltage levels without changing the

frequency.

• / 4