Classical electromagnetism
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"Classical electrodynamics" redirects here. For the textbook by J. D. Jackson, see Classical
Electrodynamics (book).
Classical electromagnetism or classical electrodynamics is a branch of theoretical physics that studies
the interactions between electric charges and currents using an extension of the classical Newtonian
model. The theory provides a description of electromagnetic phenomena whenever the relevant length
scales and field strengths are large enough that quantum mechanical effects are negligible. For small
distances and low field strengths, such interactions are better described by quantum electrodynamics.
Fundamental physical aspects of classical electrodynamics are presented in many texts, such as those
by Feynman, Leighton and Sands,[1] Griffiths,[2] Panofsky and Phillips,[3] and Jackson.[4]
History [edit]
Main article: History of electromagnetism
The physical phenomena that electromagnetism describes have been studied as separate fields since
antiquity. For example, there were many advances in the field of optics centuries before light was
understood to be an electromagnetic wave. However, the theory of electromagnetism, as it is currently
understood, grew out of Michael Faraday's experiments suggesting the existence of an electromagnetic
field and James Clerk Maxwell's use of differential equations to describe it in his A Treatise on Electricity
and Magnetism (1873). The development of electromagnetism in Europe included the development of
methods to measure voltage, current, capacitance, and resistance. For a detailed historical account,
consult Pauli,[5] Whittaker,[6] Pais,[7] and Hunt.[8]
Lorentz force [edit]
Main article: Lorentz force
The electromagnetic field exerts the following force (often called the Lorentz force) on charged particles:
where all boldfaced quantities are vectors: F is the force that a particle with charge q experiences, E is
the electric field at the location of the particle, v is the velocity of the particle, B is the magnetic field at
the location of the particle.
The above equation illustrates that the Lorentz force is the sum of two vectors. One is the cross
product of the velocity and magnetic field vectors. Based on the properties of the cross product, this
produces a vector that is perpendicular to both the velocity and magnetic field vectors. The other vector
is in the same direction as the electric field. The sum of these two vectors is the Lorentz force.
Although the equation appears to suggest that the electric and magnetic fields are independent, the
equation can be rewritten in term of four-current (instead of charge) and a single electromagnetic
tensor that represents the combined field ( ):
Jump to navigationJump to search
"Classical electrodynamics" redirects here. For the textbook by J. D. Jackson, see Classical
Electrodynamics (book).
Classical electromagnetism or classical electrodynamics is a branch of theoretical physics that studies
the interactions between electric charges and currents using an extension of the classical Newtonian
model. The theory provides a description of electromagnetic phenomena whenever the relevant length
scales and field strengths are large enough that quantum mechanical effects are negligible. For small
distances and low field strengths, such interactions are better described by quantum electrodynamics.
Fundamental physical aspects of classical electrodynamics are presented in many texts, such as those
by Feynman, Leighton and Sands,[1] Griffiths,[2] Panofsky and Phillips,[3] and Jackson.[4]
History [edit]
Main article: History of electromagnetism
The physical phenomena that electromagnetism describes have been studied as separate fields since
antiquity. For example, there were many advances in the field of optics centuries before light was
understood to be an electromagnetic wave. However, the theory of electromagnetism, as it is currently
understood, grew out of Michael Faraday's experiments suggesting the existence of an electromagnetic
field and James Clerk Maxwell's use of differential equations to describe it in his A Treatise on Electricity
and Magnetism (1873). The development of electromagnetism in Europe included the development of
methods to measure voltage, current, capacitance, and resistance. For a detailed historical account,
consult Pauli,[5] Whittaker,[6] Pais,[7] and Hunt.[8]
Lorentz force [edit]
Main article: Lorentz force
The electromagnetic field exerts the following force (often called the Lorentz force) on charged particles:
where all boldfaced quantities are vectors: F is the force that a particle with charge q experiences, E is
the electric field at the location of the particle, v is the velocity of the particle, B is the magnetic field at
the location of the particle.
The above equation illustrates that the Lorentz force is the sum of two vectors. One is the cross
product of the velocity and magnetic field vectors. Based on the properties of the cross product, this
produces a vector that is perpendicular to both the velocity and magnetic field vectors. The other vector
is in the same direction as the electric field. The sum of these two vectors is the Lorentz force.
Although the equation appears to suggest that the electric and magnetic fields are independent, the
equation can be rewritten in term of four-current (instead of charge) and a single electromagnetic
tensor that represents the combined field ( ):
