# Electromagnetic Theory

Magnetic Poles

“He who controls magnets controls the universe”

All magnets have a north and south pole. If the north (seeking) pole is brought close to the south (seeking) pole, they attract one another. If like poles are brought too close together, they desist one another. This force of the interaction between magnetic poles: F:P1 P2/d2 where P1 and P2 depict the power of the magnetic poles. D represents the distance of the magnets.

Magnetic Fields

A magnetic field is generalized by the motion of an electric charge. Electrons in the atoms of a magnet are in constant motion. There are two kinds of electron motions which produce magnetism. The first being the electron spin. The second being the electron revolution. In most magnets, the electron spin is the primary contributor to magnetism. The electron spin being; each individual electron that is spinning on its axis. The electron revolution, being the electron revolving around the atom around the magnet. Every spinning electron is a magnet. The more electrons spinning in the same direction, will produce a more powerful magnetic field. Quite contrary to this; electrons spinning in opposite directions produce a weaker magnetic field. Most atoms produce electrons spinning in opposite directions. This is why most things are not magnets. Magnetic Domains are when a magnetic field is strong enough to cause other atoms to form clusters, which line up with each other.

Electric Currents and Magnetic Fields

An electromagnetic, is a magnet that has an electrical current flowing through it. The strength of the magnet that has an electrical current flowing through it. The strength of the magnet can be increased or decreased by changing the amount of electrical current.

Electromagnetic Induction

Electromagnetic Induction was discovered by a Michael Farady and a Joseph Henry. Both independent with no knowledge of each other. Faraday in England and Henry in the United States. They discovered electric current could be created in a wire simply by moving a magnet into or out of a coil of wire. The motion of a magnet in the wire loop was the key between the wire loop and the magnetic field. The more loops that were interacting with and moving with a magnetic field, produces a greater induced voltage. The amount of voltage also depends on how rapidly the magnetic field is entering or leaving the coil. (Voltage induced- number of loops x magnetic field change/time)

Faraday’s Law summarizes electromagnetic induction. The created voltage in a coil is in proportion to the number of loops in the coil. This is then multiplied by the rate, in which the magnetic field changes within the coils. Current also depends on the inductance of the coil. Inductance measures the tendency of a coil to resist a change in the current, because the magnetism produced by one part of the coil opposes the change of the current in other parts of the coil.

Generators and Alternating Current

Rather than moving the magnet, it makes more sense to move the coil. This is best accomplished by rotating the coil in a stationary magnetic field. As the power in the magnetic field increases, the created voltage goes in one direction. When the magnetic field decreases, the created voltage goes in the opposite direction. The frequency of the alternating current that is created is equal to the frequency of the changing magnetic field within the loop. This arrangement is called a generator. The generator converts mechanical energy into electrical energy. The Transformer

An electromagnetic Induction device which consists of an input,(which is the primary) coil of wire and an output(which is the secondary) coil of wire. The primary is powered by an ac voltage source, and the secondary is connected to an external source. Changes in the primary current, produce changes in the magnetic field. This change in turn affects the secondary. Voltage is caused in the secondary by electromagnetic induction. If both coils have the same number of turns, the voltage input and output are the same. If the secondary has more turns than the primary, the secondary produces the greater voltage. And Vice Versa, if the primary has more turns than the secondary, the primary will have more voltage.

Primary Voltage/Number of primary turns=Secondary voltage/number of secondary turns

The transformer, transforms the voltage from one coil to the next. The rate in which this transfer occurs is the power output. The primary supplies what voltage the secondary needs, no more no less.

Power into primary=power out of secondary

Electric power=voltage x current

(voltage x current)primary=(voltage x current)secondary

James Clerk Maxwell in about 1860-(British Physicist) known by Maxwell’s counterpart to Faraday’s Law

A magnetic field is induced in any region of space in which an electric field is changing with time. Maxwell understood the relationship between electromagnetic waves and light. If electric charges are set into vibration in the range of frequencies that math those of light, waves are produced that are light. Light consists of electrons. Magnetic waves the eye is sensitive to.