Introduction to Marine Engineering

Conductors are materials that provide a pathway to connect the various components within the circuit, allowing the current to flow from the power source to the load.

Good conductors are materials that have low resistance because their electrons are loosely bound to their atoms. Copper, aluminum, silver, and gold, are all good conductors.

Three methods are commonly used to describe the size of wires and electrical conductors.

The American Wire Gage (AWG) system assigns a specific number to each wire size, with lower numbers representing larger wires. The system is widely used in the United States for copper and aluminum wires. For example, a common household electrical wire might be designated as 12 AWG or 14 AWG. Smaller numbers indicate thicker wires with larger cross-sectional area, capable of carrying higher current loads. Larger numbers represents thinner wires.

The Metric system simply uses the cross-sectional area of the wire measured in square millimeters (\(\text{mm}^2\)). For instance, you might see a wire labeled as \(2.5 \text{ mm}^2\) or \(4.0 \text{ mm}^2\text{.}\) A larger number indicates a larger cross-sectional area and, therefore, a thicker wire capable of carrying more current.

Circular mils. This system is used in the United States when discussing very small or very large wire sizes. The term circular mil is often abbreviated as CM. The circular mil is defined as the area of a circle with a diameter of one mil, where one mil is a unit of length equal to one thousandth of an inch (0.001 inch).