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Electrical Terms Glossary

Comprehensive reference of common electrical terms, definitions, and concepts. Perfect for students, apprentices, and professionals.

Jump to Letter:

ABCDEGIKNOPRSVW

A

Alternating Current (AC)

Electric current that reverses direction periodically. Standard in household power systems.

Unit: Amperes (A), frequency in Hertz (Hz)
Example: US household power is 120V AC at 60Hz

Ampacity

Maximum amount of current a conductor can carry continuously under specified conditions without exceeding its temperature rating.

Unit: Amperes (A)
Example: 12 AWG copper wire has ampacity of 20A in typical conditions

Ampere (Amp)

Unit of electric current. One ampere is the flow of one coulomb of charge per second.

Unit: A (Amperes)
Example: A typical LED bulb draws 0.1A (100mA)

AWG (American Wire Gauge)

Standard system for wire size measurement. Lower numbers indicate thicker wire with higher ampacity.

Example: 12 AWG is thicker than 14 AWG and can carry more current

B

Branch Circuit

Portion of wiring system extending from final overcurrent device to outlets. NEC limits voltage drop to 3% on branch circuits.

Example: Kitchen appliance circuits are typically 20A branch circuits

C

Circuit Breaker

Automatic switch that interrupts current flow when it exceeds safe levels, protecting against overload and short circuits.

Example: A 15A breaker trips when current exceeds 15 amperes

Conductor

Material that allows electric current to flow easily. Copper and aluminum are common conductors.

Example: Copper wire is the most common conductor in electrical systems

Current (I)

Flow of electric charge through a conductor. Measured in amperes.

Formula:I = V / R (Ohm's Law)
Unit: Amperes (A)
Example: A 1500W heater at 120V draws 12.5A

D

Direct Current (DC)

Electric current flowing in one constant direction. Used in batteries, electronics, and solar systems.

Unit: Amperes (A)
Example: Car batteries provide 12V DC power

E

Electrical Load

Device or appliance that consumes electrical power in a circuit.

Example: Light bulbs, motors, and heaters are electrical loads

G

Ground/Earth

Connection to the earth that provides safety path for fault currents. Protects against electric shock.

Example: Green wire in electrical cables connects to ground

I

Insulator

Material that resists electric current flow. Used to prevent unintended current paths.

Example: Rubber and plastic are common wire insulators

K

Kilowatt (kW)

Unit of power equal to 1000 watts. Commonly used for large electrical loads.

Unit: kW (1000 watts)
Example: Electric water heater typically uses 4-5 kW

Kilowatt-Hour (kWh)

Unit of energy equal to using 1 kilowatt for 1 hour. Used by utilities to measure consumption.

Unit: kWh
Example: Running a 100W bulb for 10 hours uses 1 kWh

N

NEC (National Electrical Code)

Standard for safe electrical installation in the United States. Updated every 3 years.

Example: NEC requires GFCI protection in bathrooms and kitchens

O

Ohm (Ω)

Unit of electrical resistance. One ohm allows one ampere to flow at one volt.

Unit: Ω (Ohms)
Example: A typical LED resistor is 220Ω

Ohm's Law

Fundamental relationship between voltage, current, and resistance in electrical circuits.

Formula:V = I × R
Example: 10V across 5Ω produces 2A of current

P

Parallel Circuit

Circuit where components are connected across common voltage points, providing multiple current paths.

Example: Household outlets are wired in parallel

Phase

In AC systems, refers to timing relationship of voltage/current waveforms. Single-phase (residential) or three-phase (industrial).

Example: Homes use single-phase 120V/240V service

Power (P)

Rate of energy transfer or consumption in a circuit. Product of voltage and current.

Formula:P = V × I
Unit: Watts (W)
Example: A 120V circuit with 10A draws 1200W

Power Factor

Ratio of real power to apparent power. Indicates efficiency of AC power usage.

Example: Motors typically have power factor of 0.7-0.9

R

Resistance (R)

Opposition to current flow in a conductor or component. Generates heat when current flows.

Formula:R = V / I
Unit: Ohms (Ω)
Example: Longer wires have higher resistance

Resistor

Component designed to have specific resistance. Used to limit current and divide voltage.

Example: LED circuits use resistors to limit current

S

Series Circuit

Circuit where components are connected end-to-end, providing single path for current.

Example: Old Christmas lights were wired in series

Short Circuit

Unintended low-resistance path between conductors, causing excessive current flow.

Example: Damaged wire insulation can cause short circuits

V

Voltage (V)

Electrical potential difference between two points. The "pressure" that pushes current through a circuit.

Formula:V = I × R
Unit: Volts (V)
Example: US household outlets provide 120V

Voltage Drop

Reduction in voltage along a conductor due to resistance. NEC limits this to 3% on branch circuits.

Formula:VD = 2 × K × I × L / CM
Example: Long wire runs cause more voltage drop

W

Watt (W)

Unit of electrical power. One watt is one joule per second.

Unit: W (Watts)
Example: Modern LED bulbs use 9-12W for brightness of old 60W incandescent

Wire Gauge

Measurement of wire diameter. Affects ampacity and resistance.

Example: Thicker wire (lower gauge number) carries more current

📚 Learn By Doing

Put these concepts into practice with our interactive calculators:

⚡ Ohm's Law Calculator
Understand V, I, R relationships
📉 Voltage Drop Calculator
Calculate wire resistance effects
🎨 Resistor Color Code
Decode resistor values
📐 Formula Reference
All electrical formulas
🔗

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