Energy Concepts

Basic Terms

Energy: noun- power derived from the utilization of physical or chemical resources, esp. to provide light and heat or to work machines.

Power: noun- a source or means of supplying energy.

Electricity: noun- a form of energy resulting from the existence of charged particles (such as electrons or protons), either statically as an accumulation of charge or dynamically as a current.

Energy in Daily Life

Mechanical Potential Energy

This is the energy of an object or a system due to the position of the body or the arrangement of the particles of the system. Though all stationary object possess potential energy, one example we have experienced is the pressure in an unopened soda can.

Mechanical Kinetic Energy

This is the energy of an object which it possesses due to its motion. Though all moving objects possess kinetic energy, one example we see every day is a speeding car.

Energy Units

Calorie: the approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius; applies to thermal energy.

ex) A kilocalorie is often used to describe food energy.

Joule: is the International System unit of electrical, mechanical, and thermal energy.

ex) An average person sitting quietly produces 100 J of heat every second.

Watt: defined as one joule per second; measures the rate of energy conversion or transfer; applies to thermal, electrical and mechanical energy.

ex) A typical household incandescent light bulb has a power rating of 25 to 100 watts.

BTU: British Thermal Unit; is a traditional unit of energy equal to about 1055 joules; is the amount of energy needed to cool or heat one pound of water by one degree Fahrenheit; describes the heat value (energy content) of fuels.

ex) One gallon of oil equals 140,000 BTU.

kWh: is a unit of energy equal to 1000 watt hours or 3.6 megajoules; applies to mechanical, electrical and thermal energy.

ex) The kilowatt hour is most commonly known as a billing unit for energy delivered to consumers by electric utilities.

Horsepower: is the measurement of power, the rate at which work is done; applies to electrical mechanical and thermal energy.

ex) The Ford F-150's engine has 411 horsepower.

Laws of Thermodynamics

First Law of Thermodynamics: energy can neither be created nor destroyed. It may change from one form to another, but the energy in a closed system remains constant.

ex) When a moving car hits a parked car and causes the parked car to move, energy is transferred from the moving car to the parked car.

Second Law of Thermodynamics: when energy is transferred, there will be less energy available at the end of the transfer process than at the beginning. Due to entropy, which is the measure of disorder in a closed system, all of the available energy will not be useful to the organism. Entropy increases as energy is transferred.

ex) In a diesel engine, not all energy will be available from the diesel gasoline because some will "leak" as heat and friction.

Physics - Understanding Electromagnetic induction (EMI) and electromagnetic force (EMF) - Physics


Most of the electricity in the United States is produced in steam turbines. A turbine converts the kinetic energy of a moving fluid (liquid or gas) to mechanical energy. Steam turbines have a series of blades mounted on a shaft against which steam is forced, thus rotating the shaft connected to the generator. In a fossil-fueled steam turbine, the fuel is burned in a furnace to heat water in a boiler to produce steam. The spinning blades produce kinetic energy, which is then transformed into electrical energy through the use of generators.


An electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric current to flow through an external circuit. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air, or any other source of mechanical energy. Generators provide nearly all of the power for electric power grids.

Physics 12.5.2a - DC and AC

How Electricity Makes it to Our Homes

Load Management and Power Pools

Power pooling is used to balance electrical load over a larger network (electrical grid) than a single utility. It is a mechanism for interchange of power between two and more utilities which provide or generate electricity. Load management, also known as demand side management, is the process of balancing the supply of electricity on the network with the electrical load by adjusting or controlling the load rather than the power station output. Both of these contribute to energy efficiency by allowing individual stations to work at stable outputs rather than having some power stations working at peak load while others are operating at base load.

What is Energy Efficiency?

Energy efficiency, sometimes called efficient energy use, is using less energy to provide the same level of performance, comfort, and convenience. For example, an energy efficient compact fluorescent light bulb uses 85% less energy than a conventional incandescent bulb to produce the same amount of light. Thus the compact fluorescent light bulb is much more energy efficient and will use less electricity. In general, efficient energy use is achieved by using more efficient technologies or processes rather than by changing human behavior.