Building Electrical Systems Flashcards

Vocabulary flashcards covering core concepts, components, wiring systems, and equipment in building electrical systems.

Electricity

A form of energy generated by friction, induction, or chemical change, having magnetic, chemical, and radiant effects; defined as the motion of free electrons through a solid conductor.

Dynamic Electricity

A class of electricity (electrodynamic) that flows through a substance in the form of an electric current.

Static Electricity

A class of electricity (electrostatic) characterized by stationary electric charges.

Primary Battery

An electrochemical cell or battery that delivers electricity as soon as its parts are assembled, provided it is connected to a circuit.

Secondary Battery

A storage battery through which electricity from an external source must be passed ("charging") before it can deliver an electric current.

Alternating Current Generator (Alternator)

A machine that converts mechanical energy into alternating electric current, providing the bulk of electrical energy used for power and lighting.

Direct Current Generator

A generator that furnishes direct current energy specifically for elevators, intercommunicating telephone systems, signal controls, and clock systems.

Electric Motor

A machine that converts electrical energy into mechanical energy.

Step-Up Transformer

A transformer constructed with fewer turns in the primary winding than in the secondary winding, used to transform low voltage to high voltage for transmission.

Direct Current (DC)

An electric current that flows at a constant time rate and continuously in the same direction.

Alternating Current (AC)

An electric current that periodically varies in time rate and direction, rising from zero to maximum, falling to zero, reversing direction, and returning to zero.

Coulomb

The unit of electric quantity, comprising approximately $6.25 \times 10^{18}$ electrons.

Ampere

The unit of electric current representing a rate of flow of one coulomb ($6.25 \times 10^{18}$ electrons) per second through a given cross-section.

Ampacity

The current carrying capacity of a wire or cable expressed in amperes, without undue heating.

Volt

The unit of electric potential difference or electromotive force required to move a charge of one coulomb between two points in an electric field.

Ohm

The unit of electrical resistance that allows a current of one ampere to flow when a potential difference of one volt is impressed upon it.

Impedance

The unit of opposition to current flow in an alternating-current ($\text{a-c}$) circuit, abbreviated as $Z$ and measured in ohms.

Watt

The unit of electric power representing the rate of doing electrical work.

Ohm's Law

A fundamental electrical law stating that current ($I$) in a d-c circuit is directly proportional to voltage ($V$) and inversely proportional to resistance ($R$), expressed as $I = \frac{V}{R}$.

Demand Charge

An additional electrical charge levied for power demand ($\text{kW}$) in addition to normal energy usage charges ($\text{kWh}$).

Open Circuit

An incomplete or broken electrical circuit in which conducting elements are disconnected to prevent the flow of electricity.

Short Circuit

An abnormal circuit condition resulting from bridging any part of an electrical circuit with a conductor of very low resistance.

Series Circuit

A circuit arrangement where components are connected in tandem, causing all separate loads to carry equal current, with total resistance equal to the sum of individual resistances.

Parallel Circuit

A circuit configuration in which components or loads are arranged so that current divides between them, with total current flow equal to the sum of currents through each branch.

General Purpose Branch Circuit

A branch circuit that supplies outlets for lighting and appliances, including convenience receptacles.

Appliance Branch Circuit

A branch circuit that supplies current to outlets specifically intended for feeding appliances, excluding fixed lighting.

Individual Branch Circuit

A branch circuit designed to supply power exclusively to a single specific item, such as a motor load or unit air-conditioner.

Service Entrance

The point of delivery including conductors and equipment for delivering electrical energy from the electricity supply system to the wiring system of the served building.

Service Drop

The overhead portion of service conductors extending from the nearest utility pole to a building structure.

Service Lateral

The underground portion of service conductors extending from a main power line or transformer to a building.

Main Switchboard

A freestanding assembly of switches, fuses, and circuit breakers where service entrance conductors terminate, providing control, protection, and metering of main feeders.

Feeder Circuit

A set of electrical conductors extending from the main switchboard to a distribution center or panelboard with no intermediate branch circuits connected.

Sub-feeder Circuit

An extension line of a feeder that carries power from one distribution center or cutout to another smaller sub-panelboard.

Branch Circuit

The portion of an electrical system extending from the final overcurrent device protecting a circuit to the outlets served by the circuit.

Block Diagram

A horizontal single-line diagram of a building's electrical system where major components from service entry to end utilization items are shown as blocks or rectangles.

Riser Diagram

A vertical line diagram of major electrical components that shows the spatial relationships between components across different floors of a building.

Armored Cable (Type AC)

A fabricated assembly of insulated conductors enclosed in a flexible metal sheath, commercially known by the trade name BX.

Metal Clad Cable (Type MC)

A factory-assembled cable of one or more individually insulated conductors enclosed in a metallic sheath of interlocking tape or smooth/corrugated tube.

Mineral Insulated Cable (Type MI)

A factory-assembled conductor insulated with highly compressed refractory mineral insulation enclosed in a liquid- and gas-tight continuous copper sheath.

Non-metallic Sheathed Cable (Type NM)

A factory assembly of two or more insulated conductors having a moisture-resistant, flame-retardant non-metallic outer jacket, trade-named ROMEX.

Rigid Steel Conduit (RSC)

A heavy-wall steel conduit with an approximate wall thickness of $0.117 galley\text{mm}$ ($0.117\text{ mm}$) providing maximum mechanical protection.

Intermediate Metal Conduit (IMC)

A steel conduit with an approximate wall thickness of $0.071\text{ mm}$, yielding a larger inside diameter for easier wire pulling than RSC.

Electrical Metallic Tubing (EMT)

A thin-wall unthreaded steel conduit connected using set screws or pressure fittings, not permitted in hazardous areas or embedded in concrete.

Convenience Outlet

The complete setup, including a receptacle and attachment cap, which establishes an electrical connection between a flexible cord and permanent circuit conductors.

Rheostat

A resistor used for regulating electric current or light intensity by means of variable resistance.

Contactor

A heavy-duty electrical switching device that uses blocks of silver-coated copper forced together to make or break a circuit.

Fuse

An overcurrent protective device containing a wire or strip of alloy with a low melting temperature that melts under excess current heat to interrupt the circuit.

Circuit Breaker

An overcurrent protective device equipped with thermal and magnetic trips that automatically interrupts excess current without self-destruction and can be reset manually.

Ground Fault Circuit Interrupter (GFCI)

An overcurrent protective device that detects current imbalances between ungrounded (hot) and grounded (neutral) conductors to instantaneously shut down the receptacle.

Busway

A rigid metal housing enclosing a group of insulated copper or aluminum bus bars; also referred to as a bus duct.