| A | B | C | D | E | F | G | H | I | K, L | M | N | O | P, Q | R | S | T | U, V, W , Y | |
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G |
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| Gate | In digital logic, a component that can switch the state of an output dependent on the states of one or more inputs. |
| Gibbs free energy | The Gibbs free energy is the Helmholtz free energy plus the product of the system volume and the external pressure. Changes in the Gibbs free energy at a constant pressure thus include work done against external pressure as a system undergoes volumetric changes. This proves convenient for describing equilibria in gases and liquids at a constant pressure (e.g., at one atmosphere), but is of little use in describing machine-phase chemical processes. Changes in the Gibbs free energy caused by a change in the applied pressure (at constant volume) have no direct physical significance. (See also enthalpy.) |
| Ground state | The lowest-energy state of a system. The electronic ground state of a system cannot reduce its energy by an electronic transition, but may contain vibrational energy ( kinetic and potential energy associated with the motions and positions of its atoms); extended systems at ordinary temperatures are always vibrationally excited, and so "ground state" is often taken to mean "electronic ground state." |
| Group | A set of linked atoms in a molecule; a defined substructure. Typically, a set that is usefully regarded as a unit in chemical reactions of interest. |
| Group velocity | In wave propagation, the speed of the waveform (e.g., of a peak) can be different from the speed of a group of waves (e.g., of a set of ripples in water). The latter is the group velocity, and is the speed of propagation of information and wave energy. The waveform speed is the phase velocity. |
Copyright © 1998 by John Wiley & Sons, Inc.
