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This earlier time in which an event happens such that a particle at location r 'sees' this event at a later time t is called the retarded time, t r. The retarded time varies with position; for example the retarded time at the Moon is 1.5 seconds before the current time and the retarded time on the Sun is 500 s before the current time on the Earth.
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 ...
In potential theory, an area of mathematics, a double layer potential is a solution of Laplace's equation corresponding to the electrostatic or magnetic potential associated to a dipole distribution on a closed surface S in three-dimensions.
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.
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.
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.
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]
In the case of two classical point charges, + and , with a displacement vector, , pointing from the negative charge to the positive charge, the electric dipole moment is given by =. In the presence of an electric field , such as that due to an electromagnetic wave, the two charges will experience a force in opposite directions, leading to a net ...