What is Displacement current: Definition and 53 Discussions

In electromagnetism, displacement current density is the quantity ∂D/∂t appearing in Maxwell's equations that is defined in terms of the rate of change of D, the electric displacement field. Displacement current density has the same units as electric current density, and it is a source of the magnetic field just as actual current is. However it is not an electric current of moving charges, but a time-varying electric field. In physical materials (as opposed to vacuum), there is also a contribution from the slight motion of charges bound in atoms, called dielectric polarization.
The idea was conceived by James Clerk Maxwell in his 1861 paper On Physical Lines of Force, Part III in connection with the displacement of electric particles in a dielectric medium. Maxwell added displacement current to the electric current term in Ampère's Circuital Law. In his 1865 paper A Dynamical Theory of the Electromagnetic Field Maxwell used this amended version of Ampère's Circuital Law to derive the electromagnetic wave equation. This derivation is now generally accepted as a historical landmark in physics by virtue of uniting electricity, magnetism and optics into one single unified theory. The displacement current term is now seen as a crucial addition that completed Maxwell's equations and is necessary to explain many phenomena, most particularly the existence of electromagnetic waves.

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  1. B

    Displacement current inside a wire

    The example of the charging capacitor is often used to show that Ampère's law cannot work in electrodynamics, since the value of the integral (I'm talking about Ampère in integral form here) would depend on the choice of surface delimited by the Amperian loop. It is then shown that since the...
  2. T

    Conduction and displacement current density

    Could anyone help me solve the following problem? Calculate the ratio of the conduction current density to the displacement current density of the electric field E = E_0 \cos(\omega t) in copper, to a frequence of f = 1 kHz. (Given: \epsilon_{Cu} = \epsilon_0, \rho_{Cu} = 2 \times 10^{-8}...
  3. A

    Question about displacement current and ampere's law

    A 0.230-A current is charging a capacitor that has circular plates 10.0 cm in radius. (a) If the plate separation is 4.00 mm, what is the time rate of increase of electric field between the plates? (b) What is the magnitude of the magnetic field between the plates 5.00 cm from the...
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