Dizionario elettrico

Le prime righe

0.9985 (Ayrton) 0.99941 (Boltzman.) The specific gravity of air under standard conditions 15.5° C (60° F.) and 760 mm. barometric pressure (30 inches) is taken as unity as a standard for gases. [Transcriber's note: Argon accounts for 0.9340%. It was discovered in 1894, two years after this book.] Air-Blast. (a) In the Thomson-Houston dynamo an air-blast is used to blow away the arc-producing spark liable to form between the brushes and commutator. It is the invention of Prof. Elihu Thomson. The air is supplied by a positive action rotary blower connected to the main shaft, and driven thereby. The wearing of the commutator by destructive sparking is thus prevented. A drum H H is rotated, being mounted on the axis X of the dynamo. As it rotates the three vanes are thrown out against the irregular shaped periphery of the outer case T T. The arrow shows the direction of rotation. The air is thus sent out by the apertures a a. O is the oil-cup. (b) The air-blast has also been used by Prof. Thomson in experiments with high frequency currents of high potential. By directing a blast of air against a spark discharge between ball terminals of an alternating current, the nature of the current was changed and it became capable of producing most extraordinary effects by induction. 14 STANDARD ELECTRICAL DICTIONARY. Fig. 5. AIR BLOWER FOR THOMSON'S DYNAMO. Air Condenser. A static condenser whose dielectric is air. The capacity of an air condenser in farads is equal to A / ( 4.452E12 * t ) in which A is the area of one sheet or sum of the areas of one set of connected sheets in square inches and t is the thickness of the layer of air separating them. A convenient construction given by Ayrton consists in a pile of glass plates P separated by little bits of glass F of known thickness,