EGEE 102
Energy Conservation and Environmental Protection

Forms of Energy, page 2 of 2

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Electrical Energy:

  • Energy created through the movement of electrons among the atoms of matter.
  • Although electricity is seldom used directly, it is one of the most useful and versatile forms of energy. Following are some examples. When electricity is:
    • put into a toaster, it can be converted to heat;
    • put into a stereo, it is converted into sound;
    • put into an electric bulb, it converts into light;
    • put into a motor, it converts into motion or movement (mechanical energy).
  • Due to its versatility, electricity is in high demand; in the US about 40% of the total primary energy used is converted into electricity for various uses.

Remember This!

All matter is made up of atoms, and atoms are made up of smaller particles called protons (which have positive charge), neutrons (which have neutral charge), and electrons (which are negatively charged).

  • The electrons orbit around the nucleus (which contains protons and neutrons), just like the planets orbit the sun.
  • Certain metals have electrons that are only loosely attached to their atoms, so they can be easily made to move from one atom to another if an electric field is applied to them.
  • When those electrons move among the atoms of matter, a current of electricity is created.

Nuclear Energy:

  • Energy produced when reactions occur in an atom, resulting in some type of structural change in the nuclei.
  • Fusion occurs when two small nuclei join together to create one large nucleus or particle, and during this process, energy is released in the form of light and heat. An example is in the Sun: hydrogen nuclei fuse (combine) together to make helium nuclei, which release energy.
  • Fission occurs when the nucleus of one big atom splits into two new atoms, and during this process, a tremendous amount of energy is released in the form of light and heat. An example is in a nuclear reactor or the interior of the earth: uranium nuclei split apart, causing energy to be released.

Did You Know?

In both fusion and fission, some of the matter making up the nuclei is converted into energy, represented by the famous equation:

E = mc2

Energy = Mass x (Speed of Light)2

  • This formula indicates that energy intrinsically stored in matter at rest equals its mass times the speed of light squared. When matter is destroyed, the energy stored is released.
  • This equation suggests that an incredibly huge amount of energy is released when a small amount of matter is converted to energy.

Radiation:

  • Energy radiated or transmitted in the form of rays, waves or particles. Some examples include:
    • Visible light that can be seen by naked eye;
    • Infrared radiation;
    • Ultraviolet radiation (UV) that cannot be seen with the naked eye;
    • Long wave radiation, such as TV waves and radio waves;
    • Very short waves, such as x-rays and gamma rays.
    • Even things that we encounter in our every day life contain some radioactive material either natural or man-made. Smoke detectors, compact fluorescent bulbs, some watches and granite countertops can emit some nuclear radiation. Even plane travel at high altitudes cause exposure from cosmic rays.
  • Electromagnetic Radiation
    • Energy from the sun comes to the earth in the form of Electromagnetic radiation, which is a type of energy that oscillates (side to side) and is coupled with electric and magnetic fields that travel freely through space.
    • Electromagnetic radiation is composed of photons or particles of light, which are sometimes referred to as packets of energy.
    • Photons, like all particles, have properties of waves.

Photons make the world a brighter place!

Photons are created when electrons jump to lower energy levels in atoms, and are absorbed when electrons jump to higher levels. Photons are also created when a charged particle, such as an electron or proton, is accelerated. An example of this phenomenon is a radio transmitter antenna that generates radio waves.

  • Electromagnetic Spectrum
    • The “Electromagnetic spectrum“ is a representation of the wide range of wavelengths of electromagnetic radiation.
    • Photons are associated with visible light, which accounts for only a very limited part of the electromagnetic spectrum.
    • A great discovery of the nineteenth century was that radio waves, x-rays, and gamma-rays are just forms of light, and that light is electromagnetic waves.

Please watch the following 3:20 video about the electromagnetic spectrum:

Click Here for Transcript of Electromagnetic Spectrum video

This is the diagram of the entire electro magnetic spectrum. Electro magnetic spectrum here includes all the wave lengths that we encounter. For example, the common waves that we normally use are again here the radio waves. Radio waves are long waves and microwaves are a little bit shorter here. And we have the visible light. That is the light that we use to see each other and we can see things in this range. And we have, on the other hand, on the extreme right here, the hard x-rays and gamma rays. These are the rays that we don’t see every day however, they have a lot of energy and we can feel the effects. The same way here, radio waves are long waves. A wave is: it goes up and down. Waves travel like this. The distance between the 2 peaks is the wave length. The wave length here is 10 to the 3 which is 1000 meters long. And, on this side, on the hard x-ray and gamma rays you can see the wave length is only 10 to the minus 12 which is very, very short and this also implies that the frequency, the frequency with which the wave goes up and down like this, up and down. That is the frequency is very, very low here which is only 10 to the 6th which is kind of a million times it goes up and down in a second. And on this side, where the x-rays are, you can see is 10 to the 20 which is 1 followed by 20 zero’s so the frequency is very high. Obviously, what we can say from this is as the frequency increases here the wave length is decreasing or the shorter the waves, obviously, the higher the frequency. And what we can say about energy is that theses waves which are very, very short here are in other words, very high frequency, tend to have very high energy content here. You can see energy content is measured; energy of one photon is measured here in electron volts. This is a million electron volts here for x-rays and gamma rays where as here it is 10 to the minus 9 which is one over a billion which is very, very less. So what we learned from this is, these long waves, the radio waves, etc. don’t have that much energy, whereas the x-rays and gamma rays which have high frequency and short waves, wave length, they are very high energy content and that is the reason they have very high energy content and that is why- they have very high energy content and that is the reason they can penetrate through our bodies and so on and so forth.

As depicted in the image above, the lower the energy, the longer the wavelength and lower the frequency, and vice versa.

The reason that sunlight can hurt your skin or your eyes is because it contains "ultraviolet light," which consists of high energy photons. These photons have short wavelength and high frequency, and pack enough energy in each photon to cause physical damage to your skin if they get past the outer layer of skin or the lens in your eye.

Radio waves, and the radiant heat you feel at a distance from a campfire, for example, are also forms of electromagnetic radiation, or light, except that they consist of low energy photons (long wavelength and high frequencies - in the infrared band and lower) that your eyes can't perceive. This was a great discovery of the nineteenth century - that radio waves, x-rays, and gamma-rays are just forms of light, and that light is electromagnetic waves.

About 20% of the electricity used in the US is used to produce visible light for lighting purposes.