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Introduction to Electromagnetism


History

Electric Charge

Magnetism

Practical Applications

Electrodynamics

Electro magnetic

Electric motors

Electric generators

History of light

Electromagnetic Radiation

Electronics

Quantum Electromagnetism

       

Electromagnetism: The study of affects of electric charges both at rest and in motion.
. The electromagnetic force is one of the four fundamental forces of nature and it is the main binding force of the atom outside the nucleus. Electromagnetic theory is important to understanding nature.

Electric Charge

Charge is the property of subatomic particle that gives rise to electric fields. The charge of a particle can be negative, positive, or neutral. Charge is a fundamental property of matter.

By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons
This is an illustration of a positive electric charge. The field lines are always depicted as heading away from a positive charge. This is purely a convention of the electromagnetic model. It is based on the direction of a positive charge in the field.

This is an illustration of a negative electric charge. The field lines are always depicted as heading into the negative charge. This is purely a convention of the electromagnetic model. It is based on the direction of a positive charge in the field.

Based on work by Chanchocan (Own work) [GFDL, CC-BY-SA-3.0 or CC-BY-SA-2.5-2.0-1.0], via Wikimedia Commons Based on work by Chanchocan (Own work) [GFDL, CC-BY-SA-3.0 or CC-BY-SA-2.5-2.0-1.0], via Wikimedia Commons
Put two positive charges together and the force lines repel each other bending away from the other charge. This results in the two positive charges repelling each other.

Put two negative charges together and The force lines repel each other bending away from the other charge. This results in the two negative charges repelling each other.

Based on work by Chanchocan (Own work) [GFDL, CC-BY-SA-3.0 or CC-BY-SA-2.5-2.0-1.0], via Wikimedia Commons

Put a negative and positive charge together and the force lines bend in towards the opposite charge. This results in the negative and positive charges attract each other.

This is the case for charges that are at rest with respect to each other. that is they are not moving relative to each other. When charges are moving relative to each other magnetic fields come into play.


Magnetism

Magnetism is the force of attraction or repulsion resulting from the motion of electric charges. While the force lines associated with electric charges tend to be strait, magnetic force lines tend to be circular.

By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

This is an illustration of the magnetic field around a cylindrical magnet Note that there are two poles in stead of one. The magnet force lines are depicted as going from north to south  in a circular pattern.

By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

This is an illustration of the magnetic field around antiparallel cylindrical magnets Note that each magnet has two poles in. The magnet force lines are depicted as going between the two magnets from a north pole to a south pole in a circular pattern As a result the two magnets are attracted to each other.

This is an illustration of the magnetic field around parallel cylindrical magnets. Note that each magnet has two poles in. The magnet force lines are depicted as going from the North Pole to South Pole of each magnet in a circular pattern. However they are repelling the force lines of the other magnet. As a result the two magnets are repelling each other.

By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

This is an illustration of the magnetic field around two cylindrical magnets oriented end to end and North Pole to South Pole. Note that each magnet has two poles in it. The magnet force lines are depicted as going between the two magnets from a north pole to a south pole in a circular pattern. As a result the two magnets are attracted to each other.

This is an illustration of the magnetic field around two cylindrical magnets oriented end to end and North Pole to North Pole. Note that each magnet has two poles in it. The magnet force lines are depicted as going from the North Pole to South Pole of each magnet in a circular pattern However they are repelling the force lines of the other magnet resulting in the two magnets are repelling each other.

Magnetism is seen naturally is certain rare-earth minerals and ferromagnetic material such as iron can be artificially magnetized.  The Earth has its own magnetic field as do the planets Mercury, Jupiter, Saturn, Uranus, and Neptune.

 It was the tendency of natural magnets to point north when allowed to turn freely that helped lead to the discovery of Magnetism. The other key was their ability to pick up metal objects. However the fields of permanent magnets can not be controlled.


Electrodynamics

Electrodynamics is the branch of physics dealing with the electromagnetic forces between electric charges. In its most basic form electrodynamics deals with the affect of charges in relative motion.

When an electric field is not in relative motion then you just the electric field but when this electric field is placed in relative motion the result is a magnetic field at right angles to both the electric field and relative motion. In addition a magnetic field in relative motion will in turn produce an electric field in the same directions as shown in the illustration.

A common way of determining field directions is called right hand rule. It show up several time in the field of electromagnetism To use it in this case hold you hand as shown here with the three fingers at right angles to each other.

The three vectors point as illustrated the velocity points in the direction of the thumb, the magnetic field points in the direction of the index finger and the electric field points in the direction of the middle finger.

It is this mutual production of electric and magnetic fields that  forms the  bases of the unification of eclectic and magnetic fields. Every thing else in electromagnetism extends from this starting principles.


Electromagnets

An electromagnet is a magnet whose magnetic field is produced by way of an electric current. The magnetic field of an electromagnet exists only as long as the electric current is flowing. This magnetic field ceases to exist when the electric current is turned off.

An electromagnet starts with a wire.

Induce an electric current into the wire flowing in the direction of the arrow.

The flow of the electric current produces a magnetic field even though the wire remains electrically neutral.

This is where the right hand rule again come into play. Point you thumb in the direction of the current.

Rap your hand around the wire and the magnetic field points in the direction you fingers are pointing.


By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

When the wire is bent into a loop it produces a dipole magnetic field.


By Geek3 [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

When the loop is repeats several times the result is an electromagnet. Putting a peace of iron or other ferromagnetic material in the coil called the core it increases its strength by magnetizing the core material.


Electromagnetic radiation

Electromagnetic radiation is the form of energy that charged particles absorb and emit and travels through space at the speed of light with a wave-like behavior.


By P.wormer (Own work) [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons

Electromagnetic radiation contains both electric and magnetic field components. These field components osculate in a wave-like pattern at right angles to each other  


By Inductiveload, NASA [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

This results in the electromagnetic spectrum which includes radio waves, microwaves, infrared, visible light, ultraviolet, X – rays, gamma Rays and cosmic rays. Each type of electromagnetic radiation is distinguished by wavelength.


Conclusion

Electromagnetism is one of the four fundamental forces of nature. It not only literally holds things together but it is light itself.


 

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