Alternating-currents Sentence Examples
In certain forms, hot-wire instruments are well adapted for the measurement of very small alternating currents.
The conditions permit of the circulation of the alternating currents of low periodicity, which are used for operating the bells, but in respect of the battery the circuit is open until the subscriber lifts the receiver, when the hook switch, thus released, joins the transmitter with one winding of an induction coil in series across the circuit.
The instrument can therefore be graduated by passing through it known and measured continuous currents, and it then becomes available for use with either continuous or alternating currents.
They are constructed for the measurement not only of continuousor unvarying butalsoof alternating currents.
In this form it has the advantage that it can be used for either continuous or alternating currents.Advertisement
If these conditions are not fulfilled, the wattmeter readings, assuming the wattmeter to have been calibrated with continuous currents, may be either too high or too low when alternating currents are being used.
Hot wire voltmeters, like electrostatic voltmeters, are suitable for use with alternating currents of any frequency as well as with continuous currents, since their indications depend upon the heating power of the current, which is proportional to the square of the current and therefore to the square of the difference of potential between the terminals.
This measurement is applicable to the measurement of high potentials, either alternating or continuous, provided that in the case of alternating currents the high resistance employed is wound non-inductively and an electrostatic voltmeter is used.
In 1883 Lucien Gaulard, following a line of thought opened by Jablochkov, proposed to employ high pressure alternating currents for electric distributions over wide areas by means of transformers.
An instrument of this form is valuable in measuring small alternating currents by the fall of potential produced down a known resistance.Advertisement
The instrument can be calibrated by continuous currents and may then be used for high frequency alternating currents.