How does energy move?
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
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
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.
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!
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Update: June 2012