MadSci Network: Engineering

Re: Electricity

Area: Engineering
Posted By: Gregory Paxson, Grad student Engineering, Karman
Date: Sun Mar 2 19:38:25 1997
Message ID: 847001424.Eg

Authur,  To understand how electricity gives a motor energy, you must take
a look at the properties of electricity and magnetics and the common 
bonds/reactions between the two.

First, lets put together a short definition for electricity: Electricity 
is the accumulation or movement of charged particles. All matter solid, 
liquid or gas is made of particles, some of which carry an electrical 
charge, called electrons. An electric current is the flow of negatively 
charged "free" electrons through a material. The electrons always flow 
toward the positive terminal in a circuit.

Magnetism is the magnetic force which is also produced by the motion of
charged particals such as electrons .This shows you the close relationship
between electricity and magnetism. The electron motion generated force 
creates a magnetic field, you can visualize this as looking similiar to the 
expanding ripples seen when you drop a rock in water. This magnetic field
can influence other magnetic materials without physically contacting them.
Hold a magnet close to your refrigerator, feel the pull, or rub a balloon 
on your head and see how it will stick, attract, to the wall in your room.
These are both examples of magnetism which can both attract and repel 
surrounding matter.

The close relationship between electricity and magnetism is what's in-
volved in the study of electromagnetic theory. Some of the discoverers 
were Petrus Peregrinus, William Gilbert, Charles Coulomb, Hans Oersted, 
Andre Ampere, Dominique Arago, Michael Faraday and James Maxwell. I 
recommend some reading on their discoveries for you to get a better
understanding of reactions taking place.

In this area of electromagnetics it is seen that a conductor passing 
through a magnetic field will produce an electric current or conversely
(most importantly for a motor) if a current is passed through a conductor
which is in a magnetic field, a mechanical force is produced.

Knowing these relationships we can now make the statement that an electric
motor creates movement by placing current carrying coils in a magnetic

A common motor, called an universal motor, is made up of the 3 major 
components. A stator, rotor and brushes. The stator, an electromagnet,
creates the magnetic field. The rotor consists of several coils of wire.
Brushes feed one coil with current and its resulting magnetic field
interacts with that of the stator causing the rotor to turn slightly. As 
each coil is fed in quick succession, the rotor spins. Thus you have 
taken electricity, converted it to electromagnetics, which transferred some
of its energy  to the movement of the motor shaft.

There are many types of motors each with its own design and means of 
utilizing this interaction of forces. Such as the computer you're using 
right now most likely has a stepper motor to drive the hard disk.

I hope my conversation has helped you understand a little more about motors
and their use of electricity. Take some time to look up the people I 
mentioned plus some others and keywords. Remember questions like yours 
is what leads to the great inventions, but only if you seek out the answers.


Thomas Edison		Electrons		Rotor	
Nikola Testa		Electric Current	Brushes
Charles Steinmetz	Circuit			Electricity
Magnetic Field		Magnetics		Electromagnetic
Charged Particles	Conductor		Atoms

Thanks for writing and keep asking questions.

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