## Essential Electrical and Electronic Terminology

**Ah Rating:** A capacity rating for batteries calculated by multiplying current (A) by the length of time (h) a battery can deliver that current to a load.

**Ammeter:** An instrument used to measure electrical current.

**Ampere (A):** The unit of electrical current.

**Atom:** The smallest particle of an element with its unique characteristics.

**AWG (American Wire Gauge):** A standardization based on wire diameter.

**Charge:** An electrical property resulting from an excess or deficiency of electrons; can be positive or negative.

**Circuit Breaker:** A resettable protective device for interrupting excessive current.

**Circuit:** An interconnection of electrical components designed for a specific purpose.

**Closed Circuit:** A circuit with a complete current path.

**Conductance:** The ability of a circuit to allow current; measured in Siemens (S).

**Conductor:** A material where electric current is easily established, e.g., copper.

**Coulomb (C):** The unit of electrical charge; the charge possessed by 6.25 x 10^18 electrons.

**Coulomb’s Law:** States a force between charged bodies is directly proportional to the product of charges and inversely proportional to the square of the distance between them.

**Current Source:** A device producing a constant current for a varying load.

**Current:** The rate of flow of charge (free electrons).

**DMM (Digital Multimeter):** An electronic instrument measuring voltage, current, and resistance.

**Efficiency:** The ratio of the output power to the input power of a circuit, usually expressed as a percentage.

**Electron:** A basic particle of negative electrical charge in matter.

**Energy:** The ability to do work; measured in joules (J).

**Free Electron:** A valence electron free to move within a material’s atomic structure.

**Fuel Cell:** Converts electrochemical energy into DC voltage; hydrogen fuel cells are common.

**Fuse:** A protective device burning open during excessive current.

**Ground:** The common or reference point in a circuit.

**Half-Splitting:** A troubleshooting procedure where one starts in the middle of a circuit or system and, depending on the first measurement, works toward the output or toward the input to find the fault.

**Insulator:** A material not allowing current under normal conditions.

**Joule (J):** The SI unit of energy.

**Kilowatt-Hour (kWh):** A large unit of energy mainly used by utility companies.

**Linear:** Characterized by a straight-line relationship.

**Load:** An element drawing current and on which work is done, connected across a circuit’s output.

**Ohm (Ω):** The unit of resistance.

**Ohm’s Law:** A law stating that current is directly proportional to voltage and inversely proportional to resistance.

**Ohmmeter:** An instrument measuring resistance.

**Open Circuit:** A circuit without a complete current path.

**Potentiometer:** A three-terminal variable resistor.

**Power Rating:** The maximum amount of power that a resistor can dissipate without being damaged by excessive heat buildup.

**Power Supply:** A device that converts AC from utility lines to a DC voltage.

**Power:** The rate of energy usage; measured in watts (W).

**Resistance:** Opposition to current; measured in ohms (Ω).

**Resistor:** An electrical component designed with a specific resistance.

**Rheostat:** A two-terminal variable resistor.

**Schematic:** A symbolized diagram of an electrical or aelectronic circuit.

**Semiconductor:** A material with conductance between a conductor and an insulator, e.g., silicon.

**Siemens (S):** The unit of conductance.

**Switch:** An electrical or electronic device for opening and closing a current path.

**Troubleshooting:** A systematic process of isolating, identifying, and correcting a fault in a circuit or system.

**Volt (V):** The unit of voltage or electromotive force.

**Voltage Drop:** The decrease in voltage across a resistor due to a loss of energy.

**Voltage Source:** A device producing a constant voltage for a varying load.

**Voltage:** The energy per charge available to move electrons in an electric circuit.

**Voltmeter:** An instrument measuring voltage.

**Watt (W):** The unit of power; one watt is the power when 1 J of energy is used in 1 second.

**Watt’s Law:** A law stating the relationships of power to current, voltage, and resistance.