Magnets and Electricity Generation
Name: Tricia L.
Date: June 2003
How are magnets used in a generator to produce electricity in power plants?
Generation of electricity is actually transfer of energy. I am sure you well know that the
shaft of a generator rotates and transfers its mechanical energy into electrical energy.
Let me give you a brief background on how this energy is transferred and why the mere presence
of the magnets is NOT ENOUGH to generate electricity. Of course the shaft needs to be moving
as well. WHY?
Power, induced by a magnetic field can only be transferred if it is cyclical in nature
(alternating current). Also, it should be pointed out the MAGNETS are held stationary and
a COIL is "wrapped" around the shaft in such a way that when the shaft rotates, its position
relative to the magnets rotates. THERE IS YOUR 'CYCLICAL' MAGNETIC FIELD. Remember, you can
only have power
generation by a TIME or POSITION varying magnetic field. In this case, it is a position
varying magnetic field.
To put it another way, if you were to have a magnet in your hand and were able to move the
magnet "fairly quickly" back and forth very closely to a coil of insulated copper wire, you
will most certainly generate an EMF (voltage) across the terminals of that coil.
Now consider this: The stationary magnets and the rotating coil are NOT IN ANY SORT OF
MECHANICAL CONTACT. But, if you were to attach a light bulb or some other appliance to
this generator, the shaft will most certainly "feel" a mechanical resistance to it. If
it did not create resistance to the shaft than you could, theoretically, power the entire
planets power needs with one alternator from a car. Of course, you cannot since you would
be violating the most important thermodynamic law, ENERGY CANNOT BE CREATED OR DESTROYED.
It can only be transferred from one place to another. If E truly does equal mc(squared).....
E=mc^2 ... than perhaps I should rephrase my previous statement to read; NEITHER ENERGY NOR
MATTER CAN TRULY BE DESTROYED only transferred, as governed by the above equation.
I hope this helps.
Click here to return to the Engineering Archives
Update: June 2012