Energy Glossary


Alternating current

Also known as AC power, alternating current is electricity that reverses direction within a circuit. The electricity we use in our homes does this 120 times per second.

Amperage, amps

A measurement of the amount of electric current.


Devices used in the home to perform domestic chores, such as a clothes dryer, dishwasher, refrigerator, and toaster.


The layer of gases that surrounds the earth.


The smallest unit of matter. Scientists so far have found 118 kinds of atoms. Everything in the world is made of different combinations of these atoms.



Organic materials, such as wood by-products and agricultural wastes, that can be burned to produce energy or converted into a gas and used for fuel


Carbon dioxide (CO2)

A colorless, odorless, nonpoisonous gas that is a normal part of the air we breathe. Carbon dioxide is exhaled by humans and animals, and is absorbed by green growing plants and by the sea.

CO2 emissions

The release of carbon dioxide as a result of a chemical or physical process.

Carbon footprint

The amount of carbon dioxide (CO2) that is released to the atmosphere as a result of the energy used for one’s everyday activities.

Carbon monoxide (CO)

A colorless, odorless gas produced when any fossil fuel is used improperly and burns without sufficient oxygen. CO poisoning causes flu-like symptoms and in rare cases, death. It can be prevented through proper appliance installation, maintenance, and use.


A thick paste-like substance used to fill up a crack or seam to make it watertight or airtight.

Chemical energy

Energy that is released by a chemical reaction.

Chemical reaction

A process that changes one substance into another substance. Chemical reactions that take place during digestion change energy in food into substances that the body can use to do work.


A circular path in which electricity travels.

Climate change

Changes in temperature, rainfall, wind, and other aspects of the earth’s climate that last for an extended period.

Closed circuit

An electrical circuit providing an uninterrupted, endless path for the flow of current.


A solid fossil fuel found in the earth. Coal is burned to make electricity.


The burning of a fuel and oxidant to produce heat and/or work.

Compact Fluorescent Lights

Lights that use a lot less energy than regular (incandescent) light bulbs. Also known as CFLs.

Concentrated Solar Power

CSP systems use lenses or mirrors to focus a large area of sunlight onto a small area. Electrical power is produced when the concentrated light is directed onto photovoltaic surfaces.


Something that allows electricity to flow through it easily. Water and most metals are good conductors.


A main rotating shaft running the length of the engine that transmits power to the transmission for turning the wheels of a car.


The movement or flow of electricity


Diesel engine

A type of engine invented by Dr. Rudolf Diesel at the end of the 19th century. It was originally designed to run on a variety of fuels, including vegetable oils.

Direct current

Electricity that flows in only one direction in a circuit. Batteries use direct current electricity, also known as DC power.

Distribution wires

Power lines that carry electricity through towns and neighborhoods to homes and businesses. Distribution lines can run overhead or underground.



A system formed by the interaction of a community of organisms with their environment.

Electrical energy

A form of energy that arises from the flow of electrons.


The flow of electrons.


The basic particles that orbit the nucleus of an atom. An electron has a negative electrical charge. The flow of electrons produces electricity.


The ability to change or move matter. It is sometimes also defined as the ability to do work.

Energy efficiency

Using less energy while getting more service from your appliances and equipment. You can do this by practicing energy-efficient behaviors or using energy-efficient technology, such as new energy efficient lights and appliances.


All the natural and living things around us. The earth, air, weather, plants, and animals all make up our environment.



The splitting of an atom’s nucleus to release a large amount of heat energy.

Fluorescent bulb

A light bulb that emits light because the gas inside it glows when it is charged by electricity.

Fossil fuels

Fuels formed in the ground from the remains of plants and animals. It takes millions of years to form fossil fuels. Oil, natural gas, and coal are fossil fuels. Gasoline and diesel fuel are made from fossil fuels.


Any substance that can be burned to make energy.

Fuel cell

A technology that produces electricity through a chemical reaction similar to that found in a battery.



A machine that converts mechanical energy into electrical energy.


A person studies the physical nature and history of the earth as his or her career.

Geothermal energy

Energy that is generated by converting hot water or steam from deep beneath the earth’s surface into electricity.

GFCI (Ground Fault Circuit Interrupter)

GFCIs are safety devices found on appliance cords and power outlets. If a GFCI detects electricity leaving a circuit, it quickly shuts off the electricity to prevent serious shock.


Describes an electrical system that is connected to the earth, so that any current that leaves the circuit will go to the ground. This term can also be used to describe a person or object that is connected to the earth and can thus become electricity’s path to the ground.


Large bodies of ice that move slowly down a slope or spread outward on a land surface.

Global warming

An increase in the earth’s temperature caused by human activities, such as burning fossil fuels for energy. Burning these fuels releases carbon dioxide and other gases that make the earth’s natural greenhouse effect much stronger, trapping more of the sun’s heat in our atmosphere. Global warming is causing glaciers to melt and is changing sea levels and weather patterns.

Greenhouse effect

The greenhouse effect is the rise in temperature that the earth experiences because certain gases in the atmosphere absorb and radiate heat from the sun. This process occurs naturally and has kept the earth’s temperature about 59 degrees Fahrenheit warmer than it would otherwise be. Current life on earth could not be sustained without the natural greenhouse effect. Most scientists believe global warming is happening because the greenhouse effect has become intensified by the burning of fossil fuels, which releases an excess of carbon dioxide and other gases into the atmosphere.

Greenhouse gases

Carbon dioxide, methane, and ozone. These gases form a sort of clear layer around the earth that absorbs and radiates heat from the sun.



A compound that contains only hydrogen and carbon atoms. Natural gas is a mixture of hydrocarbons.

Hydroelectricity or Hydropower

Electricity that is generated when falling water makes a turbine spin.

Hydroelectric power plants

The power plants that generate electricity when falling water makes a turbine spin.


A colorless, odorless gas that is the simplest and most common element in the universe.


Incandescent bulb

A light bulb that emits light due to the glowing of a heated filament inside it.


Something that does not allow electricity to flow through it easily. Glass and special rubber are good insulators. Insulators do not allow electricity to flow through them easily because the electrons in their atoms do not move easily from atom to atom.



1,000 watts of electricity.

Kilowatt-hour (kWh)

A unit of energy representing one kilowatt of electricity used in one hour. Electricity usage is commonly measured and billed in kilowatt hours.

Kinetic energy

The energy created by motion.



Places for trash and garbage disposal where the waste is buried between layers of earth.


Mechanical energy

The energy of motion that can move objects from place to place.


1,000,000 watts of power or 1,000 kilowatts.


A hydrocarbon gas that is the main ingredient in natural gas. Methane molecules each contain one carbon atom and four hydrogen atoms.


Natural gas

A fossil fuel found deep in the earth. Natural gas is often found with oil.


A basic particle in an atom’s nucleus that has a neutral electrical charge.

Nonrenewable fossil fuels

Fuels that can be used up because their quantity is finite – they cannot be easily made or “renewed.” Oil, natural gas, and coal are nonrenewable fossil fuels.

Nonrenewable resources

Natural resources from the earth that exist in limited supply and cannot be replaced if used up. Oil and coal are nonrenewable resources.

Nuclear energy or nuclear power

Energy that is released from the splitting of the atoms of radioactive materials (such as uranium), and then harnessed to generate electricity.


The center of an atom. The nucleus contains tiny particles called protons and neutrons. Orbiting around the nucleus are electrons.


Ocean energy

Renewable energy derived from the sea, including wave energy, tidal energy, river current, ocean current energy, and offshore wind.


A liquid fuel found deep in the earth. Gasoline and some plastics are made from oil.

Open Circuit

An incomplete electrical circuit in which no current flows.


Photovoltaic cell

A device that changes sunlight directly into electricity.


One of the components found in oil that is used for a variety of products, such as containers, kitchenware, tubing, and sheets or films for insulation. Grocery store plastic bags are also made of polyethylene.

Power line

A wire used to carry electricity. Power lines are located high overhead or buried underground.

Power plant

A place where electricity is generated.


A basic particle in an atom’s nucleus that has a positive electrical charge.


Radiant energy

Any form of energy radiating from a source, such as heat from the sun or a campfire, or light from a bulb.


Giving off energy that is emitted in the form of particles or electromagnetic radiation.

Refining facility

A facility that takes a crude substance (such as oil) and turns it into products, such as electricity, fuels, or gases.


Replaceable. If something is renewable it can be replaced or remade.

Renewable resources

Fuels that can be easily made or “renewed.” We can never use up renewable fuels. Types of renewable fuels are solar power, wind power, and hydropower.


Natural or artificial ponds or lakes used for the storage of water.


Short circuit

A defect in an electrical circuit or wiring that allows electricity to leave its normal path. For instance, this can happen if one wire in the circuit touches another wire.

Solar cells

Solar cells collect sunlight and convert it into electricity.

Solar energy

Energy from the sun.

Solar hot water collectors

Part of a solar water heating system that allows water to be heated by the sun.

Solar panel

A device that collects energy from the sun and converts it to electricity. Solar panels are also known as “modules.”

Solar power

Energy derived from the rays of the sun that is converted into electrical power.

Solar thin films

One or more thin layers of photovoltaic materials on a surface commonly known as a substrate.

Static electricity

A form of electrical energy that results from an imbalance of positive and negative charges.


A facility where transformers lower electricity’s voltage.


Having the ability to continue.


Thermal solar power

A technology for harnessing solar energy for thermal energy (heat).


A device that controls the temperature of a heating or cooling system.

Tide/wave energy

Electricity created by harnessing the power of tides or waves.

Transfer of energy

When one energy source moves or changes another source.


A device used to increase or decrease electricity’s voltage and current.


The system in an automobile that transfers energy from the engine or motor to the wheels, causing the wheels to turn.

Transmission lines

High voltage power lines used to transport electricity over long distances. These are the largest, most visible electric lines.


A device used in the generation of electricity. It has a shaft with blades at one end and electromagnets at the other. Water, steam, or some other energy source pushes the blades, which make the shaft and the magnets spin very fast. The magnet end is surrounded by heavy coils of copper wire, and the spinning magnets cause electrons in the wire to begin to move, creating electricity.



A company or other organization that provides a public service, such as supplying electricity, natural gas, or water.


Voltage, volts

A measure of the pressure under which electricity flows.


Wattage, watts

A measure of the amount of work done by a certain amount or amperage of electric current at a certain pressure or voltage.


A type of material used to seal a door or window around the edges to keep hot or cold air from coming in or out.

Wind energy

A renewable energy source that uses the force of the wind to spin turbines and generate electricity.