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Question:
How does energy move?


Replies:
I know of three ways in which energy can be transported without external help. These are :
1. Conduction - This happens when energy is transported without any transport of matter. It requires a medium. The energy is transported by by change in random vibrations of the medium. For example an iron rod when heated at one end becomes hot at the other end too. Here the vibrations of the iron atoms are responsible for this transport.
2. Convection - Here energy is transported by actual motion of the medium. An example of this is boiling water : you can see the upwelling where the hot current is hitting the surface.
3. Radiation - Energy can be transported by waves, as by sound waves or water waves. Here energy is transported by systematic vibrations of the medium, as compared to the random vibrations that are responsible for conduction. It turns out that energy can be radiated without any medium through electromagnetic waves. One manifestation of such waves is light, and as proof of this statement i will ask you to go out at night and take a good look at stars - light is coming from stars to us through space and as we all know space is emptier than the best vacuum we can produce here on earth.

Jasjeet

Hi Tammy:

I read your question and the answer there and thought that I would add a few other possibilities. Energy can also move through a shaft. Consider the hydroelectric energy conversion process. We have built large dams to hold back water in a lake. This is done to control flooding but also to generate electricity. The water is passed through pipes from the dam to a lower elevation. We can point the flowing water over some specially designed "paddles" attached to a rotor (this is called a turbine). The turbine transmits the power (or energy per unit time) to a generator which converts the energy to electricity. The electricity is then transmitted through large conductors (wires) to homes and businesses to be converted again into another form of energy. In describing an example of how energy is transmitted through a shaft I have discussed another type of transmission form of energy. Can you guess what it is? Great question! Have fun!

Dr. Dave


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