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  2. Electric dipole moment - Wikipedia

    en.wikipedia.org/wiki/Electric_dipole_moment

    A key point is that the potential of the dipole falls off faster with distance R than that of the point charge. The electric field of the dipole is the negative gradient of the potential, leading to: [ 7 ] E ( R ) = 3 ( p ⋅ R ^ ) R ^ − p 4 π ε 0 R 3 . {\displaystyle \mathbf {E} \left(\mathbf {R} \right)={\frac {3\left(\mathbf {p} \cdot ...

  3. Mathematical descriptions of the electromagnetic field

    en.wikipedia.org/wiki/Mathematical_descriptions...

    As with any wave equation, these equations lead to two types of solution: advanced potentials (which are related to the configuration of the sources at future points in time), and retarded potentials (which are related to the past configurations of the sources); the former are usually disregarded where the field is to analyzed from a causality ...

  4. Dipole - Wikipedia

    en.wikipedia.org/wiki/Dipole

    A theoretical magnetic point dipole has a magnetic field of exactly the same form as the electric field of an electric point dipole. A very small current-carrying loop is approximately a magnetic point dipole; the magnetic dipole moment of such a loop is the product of the current flowing in the loop and the (vector) area of the loop.

  5. Liénard–Wiechert potential - Wikipedia

    en.wikipedia.org/wiki/Liénard–Wiechert_potential

    The force on a particle at a given location r and time t depends in a complicated way on the position of the source particles at an earlier time t r due to the finite speed, c, at which electromagnetic information travels. A particle on Earth 'sees' a charged particle accelerate on the Moon as this acceleration happened 1.5 seconds ago, and a ...

  6. 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]

  7. Electric potential - Wikipedia

    en.wikipedia.org/wiki/Electric_potential

    The electric potential at any location, r, in a system of point charges is equal to the sum of the individual electric potentials due to every point charge in the system. This fact simplifies calculations significantly, because addition of potential (scalar) fields is much easier than addition of the electric (vector) fields.

  8. Multipole expansion - Wikipedia

    en.wikipedia.org/wiki/Multipole_expansion

    The potential V(R), due to the charge distribution, at a point R outside the charge distribution, i.e., | R | > r max, can be expanded in powers of 1/R. Two ways of making this expansion can be found in the literature: The first is a Taylor series in the Cartesian coordinates x , y , and z , while the second is in terms of spherical harmonics ...

  9. Electric potential energy - Wikipedia

    en.wikipedia.org/wiki/Electric_potential_energy

    The electrostatic potential energy of a system of three charges should not be confused with the electrostatic potential energy of Q 1 due to two charges Q 2 and Q 3, because the latter doesn't include the electrostatic potential energy of the system of the two charges Q 2 and Q 3.