ASVAB - Electronics Information

Volts

Measures potential difference between two points

Amperes (amps)

Measures number of electrons that move past a specific point in 1 sec

Ohms

Measures resistance, anything that could limit the flow of electrons

Current

Flows negative to positive. Electric charge rate of flow, typically carried by electrons, through a conductor.

Watt

Measures power, the rate at which electrical energy is consumed or transformed into another type of energy, such as light or heat

Conductors

Allow electrons to flow freely between different atoms. These valence shells have more empty spots than they have electrons

Semiconductors

Have half-full valence shells and are neither good conductors nor good insulators

Insulators

Valence shells are more than half full, poor conductors

Ohm’s Law

Current (amperes) = (Voltage (volts)) / Resistance (ohms) = I=\frac{V}{R}

Electrical circuit components

• Voltage source

• Load: source of resistance that converts electrical energy into another form of energy

• Conductors: necessary to carry current from point A to point B

Series

Only one path electrical current can take. Current flow is the same in every part of the circuit.

R_{total}=R_1+R_2+\cdots+R_{n}

Parallel

Multiple components are connected side-by-side, creating multiple paths for current to flow.

\frac{1}{R_{total}}=\frac{1}{R_1}+\frac{1}{R_2}+\cdots+\frac{1}{R_{n}}

Power

P=IV

Direct Current

Current that only and always flows in one direction

Alternating Current

Current constantly changes direction in a regular pattern

Frequency

Number of times an alternating current completes two alternations of direction per second

Impedance

(Electromotive force) / (Current)

Tip: relate to Ohm’s law in reference to AC circuits. Substitute resistance in Ohm’s law with impedance and voltage with electromotive force.

Diode

A semiconducting electrical device with two terminals that ideally allows current to flow easily through in one direction but restricts the flow of current in the opposite direction

Transistor

A semiconductor device used to amplify or switch electrical signals and power

Transformer

Consists of two coils of wire. Used to step up or step down AC voltages. The primary winding receives electrical energy from a power source, while the secondary winding provides energy at a transformed (stepped up or down) voltage to a load.

\frac{V_{p}}{V_{s}}=\frac{N_{p}}{N_{s}}=\frac{I_{s}}{I_{p}}

Energy

Watt-hours

Consider these wires live at all times

Black and brown

Neutral wires

White or grey

Failsafe wires

Green

Rectifiers

Changes alternating current to direct current

Resistor (symbol)

Battery (symbol)

AC source (symbol)

Capacitor (symbol)

Transformer (symbol)

Inductor (symbol)

Diode (symbol)

LED (symbol)

Lamp (symbol)

Fuse