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Electromagnetic Field

  1. Jul 5, 2008 #1
    An EM Field is described as follows :

    The electromagnetic field is a physical field produced by electrically charged objects. It affects the behaviour of charged objects in the vicinity of the field.

    The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction. It is one of the four fundamental forces of nature (the others are gravitation, the weak interaction, and the strong interaction).

    The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often described as the sources of the field. The way in which charges and currents interact with the electromagnetic field is described by Maxwell's equations and the Lorentz force law.

    From a classical perspective, the electromagnetic field can be regarded as a smooth, continuous field, propagated in a wavelike manner; whereas, from a quantum mechanical perspective, the field is seen as quantised, being composed of individual photons.

    I have never been a fan of giving a definition of a word by using the word you are attempting to define (a field is a field...).

    Can anyone explain to me what an EM field is? What is it made of? Is it a particle of some sort or a continuous wave or what?


    Edit: Reading Maxwell's Equations now
    Last edited: Jul 5, 2008
  2. jcsd
  3. Jul 5, 2008 #2
    They were really trying to define "electromagnetic" more than "field".

    A field is a set of numbers or vectors or somethings at every possible point in some space. In the case of fields in physics, the space we're talking about is usually our universe. So, the electromagnetic field is just a pair of vectors (electric field and magnetic field) which can be different at every point in space. It isn't "made of" anything. It's a fundamental property of the universe.
  4. Jul 7, 2008 #3

    "The EM field is the effect experienced by an object carrying electrical charges or currents, when the object is placed into the area where such EM field exists".

    The mathematical representation/formula of a certain EM field existing in a certain region of space can be used to predict the behavious of any such object.

    The existence of a EM field in a region of space can often (but not always) be traced back to the presence of "sources", which are themselves electrical charges or currents. Which leads to saying that whenever you have a charge or current, they "produce" an EM field in the surrounding region (i.e. they produce an "effect" on any other object with charges/currents if it is placed nearby).

    Same concept as with the gravitational field. The "field" is a common concept to just say that when you put an object with mass over there, it will experience a force. But it's often extremely helpful to try to "visualize" the field as a set of force lines traced in that region, to quickly guess what will happen to such objects.
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