Electronics Information
15 questions · 10 minutes
What's covered
Basic electrical theory, circuits, components, and terminology. Feeds line scores for electronics, communications, and avionics jobs.
The four quantities
Voltage (volts) is electrical pressure. Current (amperes) is flow. Resistance (ohms) opposes flow. Power (watts) is the rate of energy use.
Ohm's law and power
V = I × R, so I = V/R and R = V/I. Power P = V × I, and also P = I²R or P = V²/R. Nearly every calculation question on this subtest comes from these two formulas.
Series circuits
One path. Current is identical everywhere. Resistances add. Voltage divides across components. One break stops everything.
Parallel circuits
Multiple paths. Voltage is identical across each branch. Current divides. Total resistance is always less than the smallest single resistor — two equal resistors in parallel give half of one.
Materials
Conductors: silver, copper, gold, aluminum. Insulators: rubber, glass, plastic, dry wood, air. Semiconductors: silicon, germanium — the basis of diodes and transistors.
Components
Resistor limits current. Capacitor stores charge in an electric field, blocks DC and passes AC. Inductor stores energy in a magnetic field and resists current change. Diode passes current one way. Transformer steps AC voltage up or down. Rectifier converts AC to DC.
Safety and protection
Fuses melt to break a circuit under excess current; breakers trip and reset. The ground wire provides a low-resistance path for fault current so equipment housings never become live.
AC vs. DC
US household power is 120V AC at 60 Hz. Batteries supply DC. Wire gauge runs backwards: a smaller AWG number means thicker wire and more current capacity.
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