6 X 300), or 73 XI 08 in electrostatic measure, otherwise 2.4X1016 amperes per sq.
For the total current we have approximately 2.5 X10-" amperes per sq.
The magnet ' is wound to a resistance of amperes with accumulators).
The instrument therefore does not begin to read from zero current, but from some higher limit which, generally speaking, is about one-tenth of the maximum, so that an ammeter reading up to io amperes will not give much visible indication below i ampere.
Very convenient and accurate instruments based on the above principles have been devised by Lord Kelvin, and a large variety of these ampere balances, as they are called, suitable for measuring currents from a fraction of an ampere up to many thousands of amperes, have been constructed by that illustrious inventor.
The value of the current in amperes is then .?.
Thus the centi-ampere balance ranges from i to ioo centi-amperes, the deci-ampere balance from i to ioo deci-amperes, the ampere balance from i to ioo amperes, the deka-ampere balance from i to ioo amperes, the hecto-ampere balance from 6 to 600 amperes, and the kilo-ampere balance from ioo to 2500 amperes.
In these circumstances the current is known to have a fixed value in amperes determined by the weight attached to the instrument.
The total magnetic induction or flux corresponds to the current of electricity (practically measured in amperes); the induction or flux density B to the density of the current (number of amperes to the square centimetre of section); the magnetic permeability to the specific electric conductivity; and the line integral of the magnetic force, sometimes called the magnetomotive force, to the electro-motive force in the circuit.
The instrument exhibited by Thompson would, without undue heating, take a current of 30 amperes, which was sufficient to produce a magnetizing force of woo units.
For simplicity of calculation, the clear length of each rod between the yokes is made 12.56 (=47r) centimetres, while the coil surrounding the standard bar contains 100 turns; hence the magnetizing force due to a current of n amperes will be ion C.G.S.
In diameter the maximum elongation was nearly doubled when a current of two amperes was passing through the iron, while the " critical value " of the field was increased from 130 to 200.
A third platinum coil, wound non-inductively between the primary and the secondary, served to carry the current by which the ring was heated; a current of 4.6 amperes, with 16 volts across the terminals, was found sufficient to maintain the ring at a temperature of 11 50° C. In the ring itself was embedded a platinum-thermometer wire, from the resistance of which the temperature was determined.
Kiliani found that the sponge was produced chiefly when a weak solution, or a low current-density, was used, and that hydrogen was usually evolved simultaneously; sound deposits resulted from the use of a current-density of 200 amperes, or more, per sq.
The ore was crushed roasted, and leached with sulphuric acid (with or without ferric sulphate); the solution was purified and then electrolysed for zinc with lead anodes and with a currentdensity of 5 amperes per sq.
At 2.75 volts when diaphragms were used, or 2.5 volts when they were dispensed with, or with to amperes per sq.
In Borchers' process the chloride is heated partly by external firing, partly by the heat generated owing to the use of a currentdensity of 90 to loo amperes per sq.
Such a furnace, to take a current of 4 H.P. (say, of 60 amperes and so volts), measured externally about 6 by 6 by 7 in., and the electrodes were about o 4 in.
In diameter, while for a current of 100 H.P. (say, of 746 amperes and Too volts) it measured about 14 by 12 by 14 in., and the electrodes were about 1 .
In such a furnace a continuous current, for example, of 3000 amperes, at 50 to 60 volts, may be used at first, increasing to 5000 amperes in about half an hour.
With a current-density of 130 to 140 amperes per sq.
Hence if the galvanometer is calibrated by a potentiometer we can determine the value of this current in amperes, and knowing the value of n and V thus determine C. Various forms of commutator have been devised for effecting this charge and discharge rapidly by J.
The bath is used with a current-density of loo amperes per sq.
The electrolyte commonly contains about a lb of copper sulphate and a lb of strong sulphuric acid per gallon, and is worked with a current density of about ro amperes per sq.
At first the current is 3000 amperes at 220 volts, increasing to 9000 amperes at 20 volts after 20 hours.
If then the amperemeter scale reading was 100 it would show an error of that scale reading of minus 1.9 amperes or nearly 2%.
The principle on which the instrument works is as follows: Suppose any circuit, such as an electric motor, lamp or transformer, is receiving electric current; then the power given to that circuit reckoned in watts is measured by the product of the current flowing through the circuit in amperes and the potential difference of the ends of that circuit in volts, multiplied by a certain factor called the power factor in those cases in which the circuit is inductive and the current alternating.
The operation is conducted at a dull red heat (about 760° C. or 1400° F.), the current density being about 0.64 amperes per sq.
The current density is about 700 amperes per sq.
Of cathode surface, and the number of rods in the anode is such that each delivers 6 or 7 amperes per sq.
By Ohm'S Law, And By The Definition Of Difference Of Electric Pressure Or Potential, We Obtain The Following Alternative Expressions For The Quantity Of Heat H In Joules Generated In A Time T Seconds By A Current Of C Amperes Flowing In A Wire Of Resistance R Ohms, The Difference Of Potential Between The Ends Of The Wire Being E = Cr Volts: H=Ect=Crt=E Z T/R.
The current from a Wilde's dynamo was passed, apparently with a current density of 5 or 6 amperes per sq.
P. 51) has found that with neutral solutions a 5% solution of copper sulphate gave no good result, while with a 20% solution the best deposit was obtained with a current-density of 28 amperes per sq.
Ft.; with solutions containing 2% of sulphuric acid, the 5% solution gave good deposits with current-densities of 4 to 7.5 amperes, and the 20% solution with 11.5 to 37 amperes, per sq.
The maximum current-densities for a pure acid solution at rest were: for 15% pure copper sulphate solutions 14 to 21 amperes, and for 20% solutions 18.5 to 28 amperes, per sq.
Ft.; but when the solutions were kept in gentle motion these maxima could be increased to 21 -28 and 28-37 amperes per sq.
Of 50 to too amperes are recommended by the former, and of 300 amperes by the latter.
Whilst the jet was playing, a good deposit was formed with so high a current-density as 280 amperes per sq.
Swan has succeeded in depositing excellent copper at currentdensities exceeding moo amperes per sq.
In copper-refining practice, the current-density commonly ranges from 7.5 to 12 or 15, and occasionally to 18, amperes per sq.
The relatively electro-negative character of silver ensures that with moderate current densities no metal (other than precious metals) will be deposited with it; hence, while the solution is pure a current-density of 30 amperes per sq.
Of cathode may be used, but as copper accumulates in it, the current-density must be diminished to (say) 15 to 20 amperes per sq.