5 - MRW - Electrical Energy Fundamentals

dry cell

A battery that uses a chemical paste electrolyte.

wet cell

A battery that uses a liquid electrolyte.

series circuit

A circuit having a single path for current flow.

parallel circuit

A circuit with multiple paths available for current flow.

substation

A collection of transformers that changes the voltage of the electrical power and redistributes it along another set of conductors.

complex circuit

A combination of series and parallel circuits.

direct current (dc)

A current that always flows in one direction.

cycle

A cycle is one complete repetition of a waveform or signal. The rate at which the signal repeats itself is expressed in cycles per second, or hertz.

transformer

A device that transfers electrical energy from one circuit to another, usually at a different voltage, through electromagnetic induction.

generator

A device that uses electromagnetic induction to convert mechanical energy to electrical energy.

battery

A group of voltaic cells that are connected in series or parallel, usually contained in one case.

conductor

A material or substance that allows electrons to flow freely through it; an object having good conductivity.

insulator

A material or substance that prevents electrons from flowing freely.

basic power formula

A mathematical formula showing the relationship among power, voltage, and current. Also called Watt's law.

electron

A negatively charged particle that orbits the nucleus of an atom.

neutron

A particle with no charge in the nucleus of an atom.

alternating current (ac)

A periodic current that continuously reverses direction.

proton

A positively charged particle of an atom.

left-hand rule

A rule for determining the direction of flow in a conductor caused by electromagnetic induction. Also known as Fleming's rule.

step-down transformer

A transformer that steps down, or decreases, the voltage exiting the transformer.

step-up transformer

A transformer that steps up, or increases, the voltage exiting the transformer.

kilowatt-hour (kWh)

A unit of electrical power. One kilowatt-hour is equal to 1,000 watts being used for a 1-hour period.

joules (J)

A unit of electrical power.One joule equals one watt-second. Named after James Prescott Joule.

hertz (Hz)

A unit of frequency that equals one cycle per second. Named after Heinrich Hertz.

load

Device that converts electricity into another form of energy.

free electrons

Electrons that are loosely bound to the nucleus of an atom and can easily leave to join other atoms.

branch

One of the pathways in a parallel circuit.

energy

The ability to do work.

electrical potential

The ability to provide free electrons.

electrolyte

The chemical solution or medium that allows for the flow of electrons in a battery.

windings

The coils of wire in an electrical device. Windings are used in generators, motors, and transformers.

current (I)

The flow of electrons.

electromotive force (E or emf)

The force that causes current to flow between two objects with different electrical potential.

Watt's law (basic power formula)

The law that states the relationship among power, voltage, and current.

Ohm's law

The law that states the relationship among voltage (E), resistance (R), and current (I): E = I × R.

amperage

The measurement of the rate of flow of electrons.

cathode

The negative terminal of a battery.

resistance (R)

The opposition to the flow of electrons through a conductor.

circuit

The pathway over which electrons can move.

anode

The positive terminal of a battery.

work

The process of changing energy from one form to another, or causing an object to gain or lose energy.

electromagnetic induction

The process of producing an electromotive force by varying the magnetic field surrounding a conductor.

power (P)

The rate of doing work. Electric power is measured in watts or volt-amperes.

atom

The smallest particle of an element.

secondary winding

The transformer winding connected to the load.

volt (V)

The unit of measurement of electromotive force caused by the difference in potential between two bodies. Named after Alessandro Volta.

ohm (Ω)

The unit of measurement used to express resistance. Named after Georg Simon Ohm.

ampere (A)

The unit used in measuring amperage or current. Abbreviated as amp (plural amps). Named after André-Marie Ampère.

watt (W)

The units of measurement used in expressing power delivered to or consumed by an electrical device. Named after James Watt.

primary winding

The winding of a transformer that creates a magnetic field and is connected to the power source side.

volt-amperes (VA)

Very simply, volts multiplied by amps. The amount of power an electric system can provide or the amount of power an electrical device requires. Equivalent to watts in simple systems. Abbreviated as volt-amps.

equilibrium

When two connected bodies have the same number of electrons; a balanced condition.