Turns, Dead, of a Dynamo.
The rotations of a dynamo armature while it is building itself up or
exciting itself. The expression is a bad one, as it is likely to be
confounded with the dead turns of armature wire.
Turns, Primary Ampere-.
The ampere-turns in a primary circuit of an induction coil or
transformer. In an electric welding transformer, or in the transformer
used in the alternating current system, where efficiency is an important
element, the ampere-turns in primary and secondary for an efficiency of
100 per cent. should be equal. In the case of an experimental induction
coil other considerations outweigh that of mere efficiency. Insulation,
including security from piercing, and the production of as long a spark
as possible, are, in these cases, the controlling consideration.
[Transcriber's note: A 100 per cent efficient transformer is impossible,
but over 99 per cent is common. At room temperature there is always some
lost flux, eddy currents and resistive losses.]
Turns, Secondary Ampere-.
The ampere-turns on the secondary circuit of an induction coil or
transformer. These depend on the path provided for the current. If of
negligible inductance, such as a number of incandescent lamps would
provide, the ampere-turns should be equal to those of the primary coil.
(See Turns, Primary Ampere.)
Typewriter, Electric.
A typewriter in which the work of printing or of pressing the type faces
against the paper, or printing ribbon, is done by electro-magnetic
attraction. The keys close electric circuits, throwing the
electro-magnetic action into play. This involves the use of electricity
for what is ordinarily only a mechanical process. The strength of the
impression, however, is independent of the touch of the operator. It has
not come into very extensive use.
[Transcriber's note: IBM introduced widely used electric typewriters in
1935.]
Ultra-gaseous Matter.
Gas so rarefied that its molecules do not collide or very rarely do so.
Experiments of very striking nature have been devised by Crookes and
others to illustrate the peculiar phenomena that this matter presents.
The general lines of this work are similar to the methods used in
Geissler tube experiments, except that the vacua used are very much
higher.
When the vacuum is increased so that but one-millionth of the original
gas is left the radiant state is reached. The molecules in their kinetic
movements beat back and forth in straight lines without colliding, or
with very rare collisions. Their motions can be guided and rendered
visible by electrification. A tube or small glass bulb with platinum
electrodes sealed in it, is exhausted to the requisite degree and is
hermetically sealed by melting the glass. The electrodes are connected
to the terminals of an induction coil or other source of high tension
electrification. The molecules which come in contact with a negatively
electrified pole are repelled from it in directions normal to its
surface. They produce different phosphorescent or luminous effects in
their mutual collisions.
Thus if they are made to impinge upon glass, diamond or ruby, intense
phosphorescence is produced. A piece of platinum subjected to molecular
bombardment is brought to white heat. A movable body can be made to move
under their effects. Two streams proceeding from one negative pole repel
each other. The stream of molecules can be drawn out of their course by
a magnet.
The experiments are all done on a small scale in tubes and bulbs,
resembling to a certain extent Geissler tubes.
[Transcriber's note: These effects are caused by plasma--ionized gas and
electrons.]