ASVAB Electronics Information Practice Test 94528

Questions 5
Topics Conductive Materials, Current, Diodes, Fuses, Open & Closed Circuits

Study Guide

Conductive Materials

All conductors have resistance and the amount of resistance varies with the element. But, resistance isn't the only consideration when choosing a conductor as the most highly conductive elements like silver and gold are also more expensive and more brittle than slightly less conductive elements like copper. A balance needs to be struck between the electrical qualities of a material and its cost and durability.

Current

Current is the rate of flow of electrons per unit time and is measured in amperes (A). A coulomb (C) is the quantity of electricity conveyed in one second by a current of one ampere.

Diodes

A diode allows current to pass easily in one direction and blocks current in the other direction. Diodes are commonly used for rectification which is the conversion of alternating current (AC) into direct current (DC). Because a diode only allows current flow in one direction, it will pass either the upper or lower half of AC waves (half-wave rectification) creating pulsating DC. Multiple diodes can be connected together to utilize both halves of the AC signal in full-wave rectification.

Fuses

Fuses are thin wires that melt when the current in a circuit exceeds a preset amount. They help prevent short circuits from damaging circuit components when an unusually large current is applied to the circuit, either through component failure or spikes in applied voltage.

Open & Closed Circuits

A closed circuit is a complete loop or path that electricity follows. It consists of a source of voltage, a load, and connective conductors. If the circuit is interrupted, if a wire is disconnected or cut for example, it becomes an open circuit and no electricity will flow.