## Electricity and Electromagnetism: Theory and Applications

written by: Aggeliki K. โข edited by: Lamar Stonecypher โข updated: 10/14/2011

Undoubtedly one of the few major discoveries of humankind throughout history, electricity has changed our lives in ways our ancestors could never imagine. Study our guide and learn electricity basics that have changed our world.

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### Basic Terms

When first starting to study electrical theory, there are some basic questions that first come to mind: what is electricity, how is a current produced, and what do we mean by the words electric charge, voltage, and electric potential? The first to deal with these matters were the famous scientists of the 19th century: Nikola Tesla, Thomas Edison, Ernst Werner von Siemens, Alexander Graham Bell, Lord Kelvin, and many more. These people actually set the basis for the electrical science and engineering that ultimately changed our modern way of life.

To begin with, terms such as electricity, electric charge and electric field require a basic knowledge of atomic theory. Subatomic particles (electrons and protons) are considered to be the carriers of electric charge, an inherent property of these particles that also produces a field of forces around it known as an electric field. The resultant field exerts attractive or repulsive forces on any other charges placed within the field. The motion of these charges constitutes an electric current.

Read the following articles for an introduction to the basics, as well as the main terms of electrical theory, including: static electricity, resistance, voltage and electric potential, just to name a few.

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### Circuits

The theory discussed above has found important practical application in the design of circuits, both electrical and electronic. An electrical circuit comprises several interconnected electric components such as resistors, capacitors, and inductors that form a closed circuit. When electrical current flows through this circuit, a certain task is carried out. On the other hand, electronic circuits are far more complex, since they comprise semiconductive elements as well.

The basic law describing the behavior of these circuits is Ohm's law, which connects the resistance of an element to the current that flows through it and the potential difference across it. However, in order to study more complex electrical circuits, other laws are also necessary to use. Find out about these laws and how you can make your own electronic circuits:

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### The Principles of Electromagnetism

The first scientist to discover a direct relationship between electrical currents and magnetism was Hans Christian รrsted, back in 1821. He observed that a wire carrying an electric current is surrounded by a magnetic field that exerts a force on a compass needle. Andrรฉ-Marie Ampรจre also studied the phenomenon by observing that attractive or repulsive magnetic forces are also exerted on moving charges.

In 1831, Michael Faraday stated that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. This is known as Faraday's law of induction, and its importance lies in the fact that electricity can be produced by using this principle. It would be needless to stress the importance of this discovery. Visit the articles below to find out how these principles work:

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If you are interested in building a simple electromagnet to demonstrate the theories explained in this guide, just for fun or for educational purposes, here are a handful of articles with all the essential information to guide you through the process:

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### Electrical Generators - Motors - Transformers

An electric generator transforms mechanical energy into electrical energy by using the interaction of magnetic fields with current-carrying conductors. The phenomenon of electromagnetic induction discovered by M. Faraday is actually the basis of electric current generation. The following articles give an introduction on how this principle is used and how a modern generator works.

The reverse process is used in electric motors where electrical energy is transformed into mechanical energy. Since both generators and motors rely on the same principle, an electrical machine can be designed to operate as generator or motor according to our needs.

Transformers, on the other hand, do not transform electrical energy to another form, but rather transfer it from one circuit to another. This is possible with the use of two inductively coupled coils belonging to each of the circuits. The mutual induction effect, which is better described in the articles below, results in the production of induced voltage in the secondary winding which is proportional to its number of turns and the primary voltage.

The applications of these three devices, generators, motors, and transformers are countless:

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Electricity has changed our lives forever by allowing us to accomplish things we never imagined we could. Although it seems that we have learned it all, electricity and electromagnetism still hold many secrets yet to be discovered.

Have questions about the basic concepts of electromagnetism and how electricity is used in motors, transformers, and electrical circuits? Can you think of additional topics that we should include here? If so, please leave a comment below.