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  2. Coulomb's law - Wikipedia

    en.wikipedia.org/wiki/Coulomb's_law

    The charges must have a spherically symmetric distribution (e.g. be point charges, or a charged metal sphere). The charges must not overlap (e.g. they must be distinct point charges). The charges must be stationary with respect to a nonaccelerating frame of reference. The last of these is known as the electrostatic approximation. When movement ...

  3. 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.

  4. Surface charge - Wikipedia

    en.wikipedia.org/wiki/Surface_charge

    According to Gauss’s law, a conductor at equilibrium carrying an applied current has no charge on its interior.Instead, the entirety of the charge of the conductor resides on the surface, and can be expressed by the equation: = where E is the electric field caused by the charge on the conductor and is the permittivity of the free space.

  5. Mass-to-charge ratio - Wikipedia

    en.wikipedia.org/wiki/Mass-to-charge_ratio

    When charged particles move in electric and magnetic fields the following two laws apply: Lorentz force law: = (+),; Newton's second law of motion: = =; where F is the force applied to the ion, m is the mass of the particle, a is the acceleration, Q is the electric charge, E is the electric field, and v × B is the cross product of the ion's velocity and the magnetic flux density.

  6. Jefimenko's equations - Wikipedia

    en.wikipedia.org/wiki/Jefimenko's_equations

    The formula provides a natural generalization of the Coulomb's law for cases where the source charge is moving: = [′ ′ + ′ (′ ′) + ′] = ′ Here, and are the electric and magnetic fields respectively, is the electric charge, is the vacuum permittivity (electric field constant) and is the speed of light.

  7. Gauss's law - Wikipedia

    en.wikipedia.org/wiki/Gauss's_law

    Gauss's law makes it possible to find the distribution of electric charge: The charge in any given region of the conductor can be deduced by integrating the electric field to find the flux through a small box whose sides are perpendicular to the conductor's surface and by noting that the electric field is perpendicular to the surface, and zero ...

  8. 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 .

  9. Elementary charge - Wikipedia

    en.wikipedia.org/wiki/Elementary_charge

    Charge quantization is the principle that the charge of any object is an integer multiple of the elementary charge. Thus, an object's charge can be exactly 0 e, or exactly 1 e, −1 e, 2 e, etc., but not ⁠ 1 / 2 ⁠ e, or −3.8 e, etc. (There may be exceptions to this statement, depending on how "object" is defined; see below.)