coulomb +

(named for French chemist Charles-Augustin de Coulomb (1736-1806), who devised a method of measuring electrical quantity)

Coulomb barrier
1. The electrostatic forces within the high potential energy region of a nucleus which prevents positively charged particles from reaching the nucleus of an atom.
2. Reactions between atomic nuclei are inhibited by the need for the nuclei to overcome the repulsive force that acts between any pair of similarly charged particles.

At high temperatures, nuclei move sufficiently fast to be able to overcome the Coulomb barrier.

The greater the nuclear charge, the higher is the temperature that is required for nuclear reactions to occur.

Coulomb crystal
A structure formed by electrons trapped at a liquid helium surface at sufficiently high electron densities and low temperatures, in which the electrons occupy the points of a two-dimensional hexagonal lattice.
Coulomb damping, dry friction damping
The dissipation of energy which occurs when a particle in a vibrating system is resisted by a force whose magnitude is a constant independent of displacement and velocity, and whose direction is opposite to the direction of the velocity of the particle.
Coulomb degeneracy
Identity of the energy levels of a charged particle bound in a Coulomb (electrostatic) field for different values of the orbital angular momentum, provided that the principal quantum number and spin state are the same.
Coulomb energy
That part of the binding energy of a solid associated with the electrostatic interaction of the ions and electrons.
Coulomb excitation
1. The existence of a high-energy state within a nucleus, arising from the interaction of the nucleus and bombarding particles too weak to penetrate it.
2. Nuclear excitation caused by the time-dependent long-ranged electric field acting between colliding nuclei.

Theoretically, the Coulomb force between the positively charged colliding nuclei is well understood, and the interaction is calculable exactly.

Coulomb excitation usually is the dominant reaction in nuclear scattering, and even occurs at low bombarding energies where the separation of the nuclei is sufficiently large that the short-ranged nuclear force does not act.

Coulomb explosion
1. An explosion in which the outward driving force is the electrical repulsion of charge.
2. A process in which a molecule moving with high velocity strikes a solid and the electrons that bond the molecule are torn off rapidly in violent collisions with the electrons of the solid; as a result, the molecule is suddenly transformed into a cluster of charged atomic constituents that then separate under the influence of their mutual Coulomb repulsion.

Coulomb explosions are most commonly studied using a particle accelerator, normally employed in nuclear physics research, to produce a beam of fast molecular ions that are directed onto a solid-foil target.

Coulomb field
1. The electric field generated by a stationary-charged particle.
2. The electrostatic field around a charged particle or object.
Coulomb friction
In mechanics, a frictional force between dry stationary surfaces which is proportional to the normal force.
Coulomb gage
A gage in which the divergence of the magnetic vector potential is equal to zero.
Coulomb gauge, radiation gauge
In quantum mechanics, a noncovariant gauge (not changing with another variable) in which there are commutation relations only for the space part of the vector potential.
Coulomb potential
1. In electricity, a scalar-point function equal to the work per unit charge used against or by the Coulomb force in moving a particle bearing an infinitely small positive charge from infinity to the field of a charged particle in a vacuum.
2. A scalar point function equal to the work per unit charge done against the Coulomb force in transferring a particle bearing an infinitesimal positive charge from infinity to a point in the field of a specific charge distribution.
Coulomb scattering
1. In physics, the scattering of charged particles through their electrical interaction.
2. A collision of two charged particles in which the Coulomb force is the dominant interaction.
Coulomb's law, Law of Electrostatic Attraction
1. A law which describes the electric force between charged objects which states that:
  • Like charges repel each other and unlike charges attract each other.
  • The attraction or repulsion acts along the line between the two charges.
  • The size of the force varies inversely as the square of the distance between the two charges.
  • The size of the force is proportional to the value of each charge.
2. In physics, a law stating that the electrostatic force between two charged bodies is proportional to the product of the amount of charge on the bodies divided by the square of the distance between them.

If the bodies are oppositely charged, one positive and one negative, they are attracted toward one another; if the bodies are similarly charged, both positive or both negative, the force between them is repulsive.

Coulomb's law applies only when the charged bodies are much smaller than the distance separating them and therefore can be treated approximately as point charges.

coulomb, coul., C
The standard international unit of electric charge, to the charge that passes through any cross-section of a conductor in one second during a constant current flow of one ampere.