Electrical Systems & Wiring Flashcards
7 cards from real MTC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Systems & Wiring flashcards as text
What is the function of a shunt resistor in a marine battery monitoring system?
Answer: Creates a precise low-resistance path to measure current flow via voltage drop
A shunt resistor allows a battery monitor to calculate amperage by measuring the millivolt drop across a known low resistance value.
Shore power reverse polarity is indicated by which instrument on a properly equipped vessel?
Answer: Shore power inlet polarity indicator light
A polarity indicator light at the shore power inlet will illuminate to warn when hot and neutral conductors are reversed at the dock pedestal.
A technician measures 0.8 ohms resistance between a vessel's underwater bronze through-hull and the DC negative bus. According to ABYC, this reading indicates:
Answer: A properly bonded fitting within the acceptable limit
ABYC specifies that bonded components should measure 1 ohm or less to the common bonding point, so 0.8 ohms is within the acceptable limit.
Which type of fuse is specifically designed to protect sensitive marine electronics from voltage spikes and slow-blow conditions?
Answer: MDX slow-blow fuse
MDX slow-blow fuses tolerate brief inrush currents common when powering up electronics while still protecting against sustained overcurrent conditions.
What is the maximum allowable length for a marine DC wiring run without a dedicated overcurrent protection device at the power source?
Answer: 7 inches
ABYC E-11 requires overcurrent protection within 7 inches of the power source (battery or bus) unless the wire is protected by its location or enclosure.
When installing a marine inverter, the DC cable run between the battery bank and the inverter should be:
Answer: As short as possible with equal length positive and negative cables
Short, equal-length DC cables minimize resistance, voltage drop, and inductance problems that reduce inverter efficiency and can cause interference.
What does the term 'common bonding conductor' refer to in marine electrical systems?
Answer: A green or bare copper conductor connecting all bonded metal components to a single reference point
The common bonding conductor connects all underwater metals and major metal components to a single equipotential point, minimizing galvanic corrosion.