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Fundamental Electromagnetic Elements
Electric Charge
Electric charge is an innate property of all charged fundamental
particles and can be either positive or negative. The charged
particles that are most common in the universe are negatively
charged electrons and positively charged protons. A charged
object, such as a statically charged balloon, has an excess or
lack of electrons. When charged particles are moving, they are
known as electric currents. An example of an electric current is
the flow of electrons along an electrical wire.
Intrinsic Magnetic Moment
In contrast to electric charge, there is no evidence that magnet-
ic charge exists. However, some fundamental particles do have
an innate magnetic property known as the intrinsic magnetic
dipole moment. A particle with a magnetic moment, such as an
electron, can roughly be thought of as a very small bar magnet.
A permanent magnet is a collection of particles with aligned
magnetic moments.
Electromagnetic Field
The electromagnetic field is a physical field created by charged
particles and particles with a magnetic moment. The field itself
does not carry electric charge or magnetic moment, but it does
carry energy and momentum. The field can transfer its energy
and momentum to charged particles and particles with mag-
netic moment. This field can also occasionally create or destroy
particles. The electromagnetic field contains two components:
an electric field and a magnetic field. Both are inseparable com-
ponents of one unified field.
The electromagnetic field can take on five general forms:
• Electrostatic fields consist of a static electric field and a
negligible magnetic field. An example is the field surround-
ing a stationary, statically charged balloon.
• Magnetostatic fields consist of a static magnetic field and
a negligible electric field. An example is the field surround-
ing a stationary magnet.
• Electroquasistatic fields consist of a slowly changing elec-
tric field and a slowly changing magnetic field, with the
electric field dominating. An example is the field inside a
simple electric circuit.
• Magnetoquasistatic fields consist of a slowly changing
electric field and a slowly changing magnetic field, with the
magnetic field dominating. An example is the field inside
an electromechanical generator.
Electromagnetism (continued)
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Fig. 2: The electromagnetic spectrum, arranged by frequency (in hertz) and wavelength. (Credit: iStock)
