| Ampere's law | <physics> General equation in electromagnetism relating the magnetic field and the currents generating it. The various forms of the equation can be found in an introductory electromagnetism text. (09 Oct 1997) |
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| Angstrom's law | A substance absorbs light of the same wavelength as it emits when luminous. (05 Mar 2000) |
| Arndt's law | An obsolete law stating that weak stimuli excite physiologic activity, moderately strong ones favour it, strong ones retard it, and very strong ones arrest it. (05 Mar 2000) |
| Arrhenius law | The theory of electrolytic dissociation (1887) that became the basis of our modern understanding of electrolytes: in an electrically conductive solution (e.g., acid, base, or salt), free ions are present before electrolysis, and the proportion of molecules dissociated into ions can be calculated from measurements of electrical conductivity as well as of osmotic pressure. Synonym: Arrhenius law. (05 Mar 2000) |
| Avogadro's law | Equal volumes of gases contain equal numbers of molecules, the conditions of pressure and temperature being the same. Synonym: Ampere's postulate, Avogadro's hypothesis, Avogadro's postulate. (05 Mar 2000) |
| Baer's law | The general organ characteristics found in all members of a group appear earlier in embryogenesis than the special organ characteristics that distinguish specific members of the group; this law is the predecessor of the recapitulation theory. (05 Mar 2000) |
| Baruch's law | The effect of any hydriatric procedure is in direct proportion to the difference between the temperature of the water and that of the skin; when the temperature of the water is above or below that of the skin the effect is stimulating; when the two temperatures are the same the effect is sedative. (05 Mar 2000) |
| beer-lambert law | The equation A=ECL, where A is the absorbance at a given wavelength of light, E is the molar extinction coefficient, C is the concentration of the molar solution, and L is the length of the light path. In words, the equation means that the concentration of a substance in moles is proportional to the absorption of a given wavelength of light by a solution of the substance. The equation is used in the study of spectroscopy. (09 Oct 1997) |
| Beer's law | The intensity of a colour or of a light ray is inversely proportional to the depth of liquid through which it is transmitted; it is concluded that the absorption is dependent upon the number of molecules in the path of the ray. Compare: Beer-Lambert law. (05 Mar 2000) |
| Behring's law | Parenteral administration of serum from an immunised person provides a relative, passive immunity to that disease (i.e., prevents it, or favourably modifies its course) in a previously susceptible person. (05 Mar 2000) |
| Bell-Magendie law | The ventral spinal roots are motor, the dorsal are sensory. Synonym: Bell-Magendie law, Magendie's law. (05 Mar 2000) |
| Bell's law | The ventral spinal roots are motor, the dorsal are sensory. Synonym: Bell-Magendie law, Magendie's law. (05 Mar 2000) |
| Bernoulli's law | <physics> When friction is negligible, the velocity of flow of a gas or fluid through a tube is inversely related to its pressure against the side of the tube; i.e., velocity is greatest and pressure lowest at a point of constriction. Synonym: Bernoulli's principle, Bernoulli's theorem. (05 Mar 2000) |
| Berthollet's law | Salts in solution will always react with each other so as to form a less soluble salt, if possible. (05 Mar 2000) |
| biogenetic law | The theory that ontogeny recapitulates phylogeny, which means that one can trace the evolutionary development of a species by studying the development of an individual embryo or young of that species. The theory is still used, especially in paleontology, but has been found to not be strictly true when applied to problems in biology. (09 Oct 1997) |