Electrician Practice Tests

A branch circuit is the wiring that runs from the last overcurrent device — a breaker or fuse — out to the outlets, lights, or equipment it feeds. Conductor size has to match the breaker rating, not the other way around: a 20A breaker needs 12 AWG copper, not 14 AWG, because undersized wire heats up well before an oversized breaker ever trips.

Grounding is a separate concept from the neutral, even though both eventually bond to the same point at the service. The equipment grounding conductor exists purely to give fault current a low-impedance path back to the source — enough current flows instantly to trip the breaker, instead of leaving a metal enclosure energized and waiting for someone to touch it.

The NEC reads top-down for a reason: Chapter 1 defines terms and general rules, Chapters 2–4 cover wiring design and protection — where most exam questions live — Chapter 5 covers special occupancies, and Chapters 6–8 cover special equipment and communications. Later chapters can override earlier ones, never the reverse.

Inside an article, the general rule always comes first, exceptions after. Table 310.16 ampacity values only apply once you've confirmed insulation type, ambient temperature, and how many current-carrying conductors share the raceway — skip one of those adjustment steps and you'll read the table wrong, even if you found the right row.

A compressor pressurizes refrigerant vapor, which forces it to reject heat and condense into a liquid. An expansion device then drops that liquid's pressure so it can boil at a low temperature and absorb heat again — that's the entire refrigeration cycle, repeated continuously.

The EPA regulates handling because most refrigerants are potent greenhouse gases — ranked by GWP (global warming potential) — or ozone-depleting, ranked by ODP. Recovery equipment exists specifically to pull refrigerant out of a system into a cylinder instead of venting it to atmosphere; venting is the exact act the certification exam is built to prevent.

A single-phase motor can't generate rotational torque from one winding's alternating field alone — it needs a second, phase-shifted current to get moving. A start capacitor provides that phase shift just long enough to spin the motor up, then drops out; a run capacitor stays in the circuit permanently, correcting the phase angle between voltage and current to cut amp draw and heat during normal operation.

Contactors and relays exist to solve a different problem: switching a high-voltage, high-current load — a compressor or condenser fan — using a low-voltage control circuit a thermostat can safely handle.

Voltage, current, and resistance are linked by one equation: V = I × R. Voltage is the electrical pressure pushing electrons through a circuit, current is how fast they flow, and resistance is what opposes that flow. Push more voltage through the same resistance and current rises proportionally; add resistance for a given voltage and current drops.

The relationship changes with circuit type: in a series circuit, current is identical through every component while voltage divides across them; in a parallel circuit, voltage is identical across every branch while current divides. Nearly every load calculation an electrician does traces back to this.