An Etymological Dictionary of Astronomy and Astrophysics
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The unit of → electric charge in the → mks system, equal to the quantity of charge transferred in one second by a steady current of one → ampere. One coulomb represents a charge of approximately 6.241 506 × 10¹⁸ → electrons. Compared with the charge unit in the → cgs system, 1 C = 2.998 × 10⁹ → esu.

Named after the French physicist Charles Augustin de Coulomb (1736-1806), who pioneered research into magnetism and electricity.

The energy barrier due to electrostatic interaction that two nuclei (for example two protons) need to overcome so they can get close enough to undergo nuclear fusion (to form a helium).

→ coulomb; → barrier.

A particle → collision where the dominant force is described by → Coulomb's law. The collision results in deflections of the particles away from their initial paths.

→ coulomb; → collision.

The → potential energy from which derives the repulsive electrostatic force between two → charged particles. For example, the Coulomb energy between two protons is e²/r ~ 0.5 MeV, which is small compared with the average → binding energy per particle (~ 8 Mev). However the Coulomb repulsion becomes important for heavy nuclei. The total Coulomb energy of a nucleus is given by: (3/5) Z(Z - 1)e²/R, where Z is the → atomic number, e the charge, and R the nuclear radius. Since R ∝ A^1/3 and Z is roughly proportional to A, the Coulomb energy is roughly proportional to A^5/3. On the other hand, the total binding energy is proportional to A, which means that the relative importance of the repulsive electrostatic energy increases with increasing mass number as A^2/3.

→ coulomb; → energy.

The transition to a higher → energy level than → ground state undergone by an atomic nucleus when a → charged particle of appropriate energy moves past it.

→ coulomb; → excitation.

An attractive or repulsive → electrostatic force between objects bearing electric charge, as described by → Coulomb's law. If the charges are of opposite sign, then the force is attractive; if thy are of the same sign, the force is repulsive.

→ Coulomb; → force.

The optimum → gauge for steady fields, defined by: ∇.A = 0, where A is the → magnetic vector potential. Also called transverse gauge.

→ Coulomb; → gauge.

The reciprocal force between two or more → charged particles according to → Coulomb's law.

→ coulomb; → interaction.

The repulsive interaction due to the → Coulomb energy between two ions. If the ionic charge is Z, then the Coulomb potential energy is Z²e²/a, where a is some typical separation between the ions. The Coulomb pressure is expected to become important when the ratio Γ_C = Z²e²/akT is much larger than 1. In that case, Coulomb effects dominate those of → thermal agitation and the gas settles down into a → crystal.

→ Coulomb; → pressure.

The electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the separation distance between the two objects

→ coulomb; → law.

The → Coulomb interaction reduced owing to the presence of other electrons. See → shielding effect.

→ screen; → coulomb; → interaction.

A unit of → electric charge in the electrostatic → cgs system of units; equal to the charge that exerts a force of 1 → dyne on an equal charge at a distance of 1 cm under vacuum; equal to 3.3356 x 10^-10 → coulombs. Same as → electrostatic unit (esu).

→ stat-; → coulomb.