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  2. Charge density - Wikipedia

    en.wikipedia.org/wiki/Charge_density

    Linear charge density (λ) is the quantity of charge per unit length, measured in coulombs per meter (C⋅m −1), at any point on a line charge distribution. Charge density can be either positive or negative, since electric charge can be either positive or negative. Like mass density, charge density can vary with position.

  3. 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.

  4. Surface charge - Wikipedia

    en.wikipedia.org/wiki/Surface_charge

    A surface charge is an electric charge present on a two-dimensional surface. These electric charges are constrained on this 2-D surface, and surface charge density , measured in coulombs per square meter (C•m −2 ), is used to describe the charge distribution on the surface.

  5. Charge (physics) - Wikipedia

    en.wikipedia.org/wiki/Charge_(physics)

    In physics, a charge is any of many different quantities, such as the electric charge in electromagnetism or the color charge in quantum chromodynamics. Charges correspond to the time-invariant generators of a symmetry group , and specifically, to the generators that commute with the Hamiltonian .

  6. 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 nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.

  7. Retarded potential - Wikipedia

    en.wikipedia.org/wiki/Retarded_potential

    Position vectors r and r′ used in the calculation. The starting point is Maxwell's equations in the potential formulation using the Lorenz gauge: =, = where φ(r, t) is the electric potential and A(r, t) is the magnetic vector potential, for an arbitrary source of charge density ρ(r, t) and current density J(r, t), and is the D'Alembert operator. [2]

  8. Electric charge - Wikipedia

    en.wikipedia.org/wiki/Electric_charge

    Electric charge (symbol q, sometimes Q) is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be positive or negative. Like charges repel each other and unlike charges attract each other. An object with no net charge is referred to as electrically neutral.

  9. Retarded time - Wikipedia

    en.wikipedia.org/wiki/Retarded_time

    Position vectors r and r′ used in the calculation. Retarded time t r or t′ is calculated with a "speed-distance-time" calculation for EM fields.. If the EM field is radiated at position vector r′ (within the source charge distribution), and an observer at position r measures the EM field at time t, the time delay for the field to travel from the charge distribution to the observer is |r ...