Electromagnetism is a theory unified by James Maxwell to explain the interrelationship between electricity and magnetism. At the heart of this theory is the notion of an electromagnetic field. A stationary electromagnetic field stays bound to its origin. Examples of stationary fields are: the magnetic field around a current carrying wire or the electric field between the plates of a capacitor. A changing electromagnetic field propagates away from its origin in the form of a wave. These waves travel at the speed of light and exist in a wide spectrum of wavelengths. Examples of the dynamic fields of electromagnetic radiation: radio waves, microwaves, light, x-rays and gamma rays. In the field of particle physics this electromagnetic radiation is the manifestation of the electromagnetic interaction between charged particles. The subfield of electromagnetism dealing specifically with the rapidly changing electric and magnetic fields which constitute light, is called electrodynamics. The whole of electromagnetism is governed by Maxwell's equations, which are compatible with and served as a motivation for the theory of relativity. The interaction of electrical and magnetic effect is known as electromagnetism. Electromagnetism is one of the most important concepts in physical science, and much of our current technology is directly related to this crucial intercourse. We can summarize the two basic principles of Electromagnetism as follows: One of the most significant application of this principle is called an electromagnet. An electromagnet consists of a current-carrying coil of insulated wire wrapped about a piece of soft iron. At what time the current is turned on, a magnet field is created inside the coil. The soft iron is magnetized by this field and makes the magnetic field nearly 2000 times stronger. When the current is turned off, the iron loses nearly all of its magnetism. The advantages of the electromagnet are numerous. First, it can be switched on and off. Second, the strength of the electromagnet can be controlled by the amount of current flowing in the wire. Third, reversing the current can reverse the poles of the magnet field. Electromagnets are used in a variety of devices and appliances, such as doorbells and telephones, and in devices used for moving magnetic metals. The mechanism in a telephone receiver will serve as an illustration of one use.
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