MTC Marine Technician Electrical & Electronics 3 — Questions and Answers
Question 1: What is 'galvanic corrosion' in a marine electrical context?
- Corrosion caused by AC leakage current through the water
- Electrochemical deterioration when two dissimilar metals are electrically connected in an electrolyte (Correct answer)
- Rust formation on iron components due to high humidity
- Oxidation of battery terminals from outgassing
Correct answer: Electrochemical deterioration when two dissimilar metals are electrically connected in an electrolyte
Galvanic corrosion occurs when dissimilar metals form an electrochemical cell in seawater, causing the more active (anodic) metal to corrode preferentially.
Question 2: The NMEA 2000 (N2K) network uses which physical layer standard?
- RS-232 serial
- Ethernet IEEE 802.3
- CAN bus (Controller Area Network) (Correct answer)
- USB 2.0
Correct answer: CAN bus (Controller Area Network)
NMEA 2000 is built on the CAN bus physical layer, allowing multiple devices to share data on a single backbone cable.
Question 3: When testing a marine battery with a load tester, a fully charged 12V battery that drops below _______ under load is considered failed.
- 11.5V
- 9.6V
- 10.5V (Correct answer)
- 12.0V
Correct answer: 10.5V
A healthy 12V battery should maintain at or above 10.5V under a half-rated load test for 15 seconds; below that indicates sulfation or cell failure.
Question 4: A marine autopilot's fluxgate compass measures:
- GPS satellite signal strength
- The Earth's magnetic field to determine heading (Correct answer)
- Boat speed through water
- Rudder angle feedback
Correct answer: The Earth's magnetic field to determine heading
A fluxgate compass detects the horizontal component of Earth's magnetic field using inductive coils to determine the vessel's magnetic heading.
Question 5: Shore power reverse polarity on a 120V AC system is MOST dangerous because it:
- Increases power consumption by 15%
- Energizes the neutral conductor, creating shock hazard even with devices switched off (Correct answer)
- Causes immediate tripping of the main breaker
- Reduces available amperage by half
Correct answer: Energizes the neutral conductor, creating shock hazard even with devices switched off
Reverse polarity puts line voltage on the neutral, meaning equipment chassis and switch contacts that appear 'off' can still be energized at full voltage.
Question 6: What is the function of a marine isolation transformer in shore power systems?
- Steps up 120V to 240V for large appliances
- Electrically separates the boat's AC system from shore ground, eliminating stray current corrosion (Correct answer)
- Converts AC to DC for battery charging
- Reduces voltage fluctuations from the dock pedestal
Correct answer: Electrically separates the boat's AC system from shore ground, eliminating stray current corrosion
An isolation transformer breaks the galvanic connection between shore ground and the boat's bonding system, preventing stray current corrosion.
Question 7: What does 'AIS' stand for in marine electronics?
- Automatic Identification System (Correct answer)
- Analog Instrument Standard
- Aquatic Interference Suppressor
- Advanced Ignition Sequencer
Correct answer: Automatic Identification System
AIS (Automatic Identification System) transmits and receives vessel identity, position, speed, and course data via VHF radio for collision avoidance.
MTC Marine Technician Electrical & Electronics 3
What is 'galvanic corrosion' in a marine electrical context?