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  2. Current density - Wikipedia

    en.wikipedia.org/wiki/Current_density

    In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. [1] The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point.

  3. Probability current - Wikipedia

    en.wikipedia.org/wiki/Probability_current

    In quantum mechanics, the probability current (sometimes called probability flux) is a mathematical quantity describing the flow of probability.Specifically, if one thinks of probability as a heterogeneous fluid, then the probability current is the rate of flow of this fluid.

  4. Maxwell's equations - Wikipedia

    en.wikipedia.org/wiki/Maxwell's_equations

    The equations introduce the electric field, E, a vector field, and the magnetic field, B, a pseudovector field, each generally having a time and location dependence. The sources are the total electric charge density (total charge per unit volume), ρ, and; the total electric current density (total current per unit area), J.

  5. List of electromagnetism equations - Wikipedia

    en.wikipedia.org/wiki/List_of_electromagnetism...

    Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal n̂, d is the dipole moment between two point charges, the volume density of these is the polarization density P.

  6. Electric current - Wikipedia

    en.wikipedia.org/wiki/Electric_current

    For negative charges, the sign of the current density is opposite to the velocity of the charges. [2]: 749 In SI units, current density (symbol: j) is expressed in the SI base units of amperes per square metre. [4]: 22 In linear materials such as metals, and under low frequencies, the current density across the conductor surface is uniform.

  7. Poynting vector - Wikipedia

    en.wikipedia.org/wiki/Poynting_vector

    The corresponding form of Poynting's theorem is =, where J is the total current density and the energy density u is given by = (| | + | |), where ε 0 is the vacuum permittivity. It can be derived directly from Maxwell's equations in terms of total charge and current and the Lorentz force law only.

  8. Gauss's law - Wikipedia

    en.wikipedia.org/wiki/Gauss's_law

    In physics (specifically electromagnetism), Gauss's law, also known as Gauss's flux theorem (or sometimes Gauss's theorem), is one of Maxwell's equations. It is an application of the divergence theorem , and it relates the distribution of electric charge to the resulting electric field .

  9. Ohm's law - Wikipedia

    en.wikipedia.org/wiki/Ohm's_law

    Ohm's law states that the electric current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, [1] one arrives at the three mathematical equations used to describe this relationship: [2]