Electrometer sentence example
An electrometer is an instrument for measuring difference of potential, which operates by means of electrostatic force and gives the measurement either in arbitrary or in absolute units.
In the last case the instrument is called an absolute electrometer.
It may be pointed out that such an arrangement is not merely an arbitrary electrometer, but may become an absolute electrometer within certain rough limits.
His portable electrometer is shown in fig.
The height of the walls in the various observatories, the height of the collectors, and the distance they project from the wall vary largely, and sometimes electrometer, and they sometimes leave hardly a trace on the photographic paper.Advertisement
A voltmeter is therefore one form of electrometer, but the term is generally employed to describe the instrument which indicates on a scale, not merely in arbitrary units but directly in volts, the potential difference of its terminals.
The principles of telegraphy (land, submarine and wireless) and of telephony are discussed in the articles Telegraph and Telephone, and various electrical instruments are treated in separate articles such as Amperemeter; Electrometer; Galvanometer; Voltmeter; Wheatstone'S Bridge; Potentiometer; Meter, Electric; Electrophorus; Leyden Jar; &C.
The accuracy of his measurement, by which he established within 2% the above law, was only limited by the sensibility, or rather insensibility, of the pith ball electrometer, which was his only means of detecting the electric charge.2 In the accuracy of his quantitative measurements and the range of his researches and his combination of mathematical and physical knowledge, Cavendish may not inaptly be described as the Kelvin of the 18th century.
He ascertained the distribution of electricity among several spheres (whether equal or unequal) placed in contact in a straight line; and he measured the distribution of 2 In 1878 Clerk Maxwell repeated Cavendish's experiments with improved apparatus and the employment of a Kelvin quadrant electrometer as a means of detecting the absence of charge on the inner conductor after it had been connected to the outer case, and was thus able to show that if the law of electric attraction varies inversely as the nth power of the distance, then the exponent n must have a value of 2 t Isua.
Snow-Harris found that this charge varied as the square root of the weight in the opposite pan, thus showing that the 1 It is probable that an experiment of this kind had been made as far back as 1746 by Daniel Gralath, of Danzig, who has some claims to have suggested the word " electrometer " in connexion with it.Advertisement
Symmetrical Electrometers include the dry pile electrometer and Kelvin's quadrant electrometer.
In the dry pile electrometer a single gold-leaf is hung up between two plates which are connected to the opposite terminals of a dry pile so that a certain constant difference of potential exists between these plates.
A vast improvement in this instrument was made by the invention of the quadrant electrometer by Lord Kelvin, which is the most sensitive form of electrometer yet devised.
They found from observations that the particular quadrant electrometer they used might be made to follow one or other of three distinct laws.
In other words, the electrometer nearly obeyed the theoretical law.Advertisement
Guided by these experiments, Ayrton, Perry and Sumpner constructed an improved unifilar quadrant electrometer which was not only more sensitive than the White pattern, but fulfilled the theoretical law of working.
The importance of this investigation resides in the fact that an electrometer of the above pattern can be used as a wattmeter, provided that the deflection of the needle is proportional to the potential difference of the quadrants.
Blondlot and P. Curie afterwards suggested that a single electrometer could be constructed with two pairs of quadrants and a duplicate needle on one stem, so as to make two readings simultaneously and produce a deflection proportional at once to the power being taken up in the inductive circuit.
In this last case, however, the capacity of the electrometer used must be small, otherwise an error is introduced.'
He has constructed a capillary electrometer by which differences of electric potential less than o oi of that of a Daniell's cell can be detected by the difference of the pressure required to force the mercury to a given point of a fine capillary tube.Advertisement
It would be theoretically possible to measure the absolute value in some metal by observing with an electrometer the P.D.
Some account of Thomson's electrometer is given in the article on that subject, while every modern work of importance on electric lighting describes the instruments which he has specially designed for central station work; and it may be said that there is no quantity which the electrical engineer is ordinarily called upon to measure for which Lord Kelvin did not construct the suitable instrument.
The invention of the portable electrometer and the water-dropping electrograph by Lord Kelvin in the middle of the 19th century, and the greater definiteness thus introduced into observational results, were notable events.
Exactly What The Potential Changes Amount To Under Such Circumstances It Is Impossible To Say; What The Trace Shows Depends Largely On The Type Of Electrometer.
The instrument consists of a high-voltage continuous-current dynamo which creates a potential difference between the needle and the two quadrants of a quadrant electrometer (see Electrometer).Advertisement
His ampere-balances, voltmeters and electrometers, and double bridge, are elsewhere described in detail (see Amperemeter; Electrometer, and Wheatstone'S Bridge).
The gold-leaf electroscope invented by Abraham Bennet (see Electroscope) can in like manner, by the addition of a scale to observe the divergence of the gold-leaves, be made a repulsion electrometer.
The conclusion to which the above observers came was that any quadrant electrometer made in any manner does not See Maxwell, Electricity and Magnetism (2nd ed., Oxford, 1881), vol.
On the other hand, it is commonly thought that the single potentialdifferences at the surface of metals and electrolytes have been determined by methods based on the use of the capillary electrometer and on others depending on what is called a dropping electrode, that is, mercury dropping rapidly into an electrolyte and forming a cell with the mercury at rest in the bottom of the vessel.