Electronics Information Study Guide for McGraw-Hill's ASVAB (page 4)

By — McGraw-Hill Professional
Updated on Jun 26, 2011

Grounding Systems

Electricity always "wants" to complete a circuit, to get back to where it came from. The wiring in a building always includes two options for returning current to the circuit breaker or fuse box. The white (grounded) wire is the normal return path for electricity. The bare (equipment grounding) wire is the alternative path, available if something goes wrong with the grounded wire. In many systems, the alternative return path is provided by a steel sheath on the wires, called a conduit.

Grounding Systems

Because the two supply wires are different (black brings the current, and white drains it away), modern electric plugs are polarized.This means that they can fit into the socket in only one way, because one lug on the plug is bigger than the other.

Grounding Systems

Switches and Rheostats

Switches turn electric circuits on and off. One single-pole switch controls a circuit. Two three-wayswitches can work together to control a circuit from either of two locations, such as at the top and bottom of a stairway. A rheostat continuously controls the voltage, and is used to dim lights. In home wiring, switches always control the hot side of the circuit—the one that supplies the current.

Electrical Connections

Electrical connections must be secure and tight. Otherwise, electric arcs will develop, causing heat and ruining the connection. One of the best connections comes from solder, a metal that is melted over a connection. Solder joints must have flux, a chemical that prevents oxidation from happening when the wires get heated. Solder can be used to join wires to other wires or wires to terminals.

Circuit Breakers and Fuses

Because electric circuits get hot when something goes wrong, circuit breakers and fuses are used in most circuits. Both have the same job: breaking the circuit (cutting off the power) when something goes wrong. A circuit breaker usually has an electromagnet that opens a circuit when the current gets too high. A fuse has an element that melts when the current is too high. Fuses are easier to make, but circuit breakers can just be reset after they trip, whereas a fuse must be replaced. If a fuse continually blows, do not replace it with a larger-capacity fuse; this invites fire. Find the problem and fix it.

Coaxial Cables

Coaxial means "having the same axis." Coaxial cables, usually used in cable TV systems, have an inner and an outer conductor.

Practice problems for this study guide can be found at:

Electronics Information Practice Problems for McGraw-Hill's ASVAB

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