| 单词 | electromotive |
| 例句 | We thus use the name electromotive force, abbreviated emf. College Physics for AP Courses 2015-08-12T00:00:00Z Kirchhoff’s Loop Rule states that the sum of the voltage drops across resistors, inductors, and capacitors is equal to the total electromotive force in a closed circuit. Calculus, Vol 2 2016-03-30T00:00:00Z As long as all the grid-connected generators are balanced with the power demand on the grid, the torque applied by the turbine is precisely balanced by the electromotive force in the coils. What Is The Holding Capacity Of The US Power Grid? 2013-10-07T16:58:00Z He went on to show that the total heat produced in any voltaic circuit was proportional to the electromotive force E of the battery and to the number of equivalents electrolysed in it. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z The disk is now turned at a measured speed about its axis, so that the electromotive force due to the cutting of the field tends to produce a current in the standard coil of wire. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z When the arc is lengthened, the electromotive force rises in proportion and the arc appears to be more persistent. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z Applying Kirchhoff’s Loop Rule to this circuit, we let E denote the electromotive force supplied by the voltage generator. Calculus, Vol 2 2016-03-30T00:00:00Z Whatever sets up the electric disturbance, whether it be the action of sulphuric acid on zinc, or caustic potash on iron, etc., is called electromotive force, generally abbreviated E.M.F. Electric Bells and All About Them A Practical Book for Practical Men 2012-03-06T03:00:25.273Z Faraday had shown that electromotive force depends on chemical affinity. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z But ordinary cable working is quite slow enough to enable such electromotive forces to be disregarded. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z The fundamental idea in these experiments is to set up an electromotive force in a vacuum tube—-preferably devoid of any electrodes—by means of electro-magnetic induction, and to excite the tube in this manner. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z The electromotive force thus generated is measured by a galvanometer, the scale of which is divided and figured so that the temperature may be directly read. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 1 "Gichtel, Johann" to "Glory" 2012-01-11T03:00:20.463Z The current, or amplitude of the continuous vibrations kept up in the circuit, depends upon two things: 1st, the electromotive force; 2nd, the resistance in the circuit. Electric Bells and All About Them A Practical Book for Practical Men 2012-03-06T03:00:25.273Z Joule measured the corresponding heats of combustion, and showed that the electromotive force corresponding to a chemical reaction is proportional to the heat of combustion of the electrochemical equivalent. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z By properly summing up the whole heat-equivalents a net total was obtained which, according to Thomson, was the energy consumed in the passage of unit current, and was therefore the electromotive force. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z Wet blotting paper is a sufficiently good conductor to screen off a stationary electrostatic effect, though it is not a good enough one to stop waves of alternating electromotive intensity. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z We have next to consider the appliances for creating the necessary charging electromotive force, and for storing and releasing this charge at pleasure, so as to generate the required electrical oscillations in the aerial. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z There must be a steadily maintained electric pressure, known under different aspects as “electromotive force,” “potential difference,” or “voltage.” Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z The watt is the work per second done by an electromotive force of 1 volt in driving a current of 1 ampere, and is equal to 10 million ergs or 1 joule per second. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z Any electromotive force otherwise produced, which gave rise to the same current, must obviously be equal to Ilv, so that the unit of electromotive force can thus be properly defined. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z It is easy to raise the electromotive force of the machine to many times the original value by simply adjusting the capacity of a condenser connected in the induced circuit. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z The Wehnelt break acts best as an interrupter with an electromotive force from 40 to 80 volts. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The necessary electromotive force or voltage required to cause the current to flow may be obtained: 1. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z Law of electric circuits, Ohm's law, current strength equals electromotive force divided by resistance of the circuit—George S. Ohm, Germany. The Story of Great Inventions 2011-10-05T02:00:16.353Z Thomson used a foot-grain-second system of units; but from this arrangement are now obtained the C.G.S. units of electromotive force and resistance. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z In such case the starting of the motor is more difficult, and the dead and inductive resistances must take up a considerable proportion of the electromotive force of the circuits. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z The first class includes all those that depend for their action on the "coherer principle" or the reduction of the resistance of a metallic microphone by the action of electromotive force. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z When the current flows, the zinc strip is observed to waste away, its consumption in fact furnishing the energy or electromotive force required to drive the current through the cell and the connecting wire. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z This leaves outstanding, however, the use of the word force in the phrase—the forces of nature—gravitative force, cohesive force, electromotive force, and so on. Spencer's Philosophy of Science The Herbert Spencer Lecture Delivered at the Museum 7 November, 1913 2011-09-25T02:00:15.883Z The temperature of maximum electromotive force was found to be independent of the temperature of the colder junction. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z On the operation of the machine, alternating currents will be developed in the circuit, and the phases of these currents will theoretically coincide with the phases of the impressed electromotive force. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z It can be accomplished by the application of any high electromotive force. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z It weakens the current by setting up an opposing electromotive force41. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z By the sensitiveness of the 430 galvanometer is meant the deflexion produced by a known electromotive force put upon its terminals or a known current sent through it. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 4 "G" to "Gaskell, Elizabeth" 2011-08-24T02:00:20.690Z It is the resistance of the circuit of slider, rails, and connecting wire, when with this electromagnetic unit of electromotive force the unit of current is made to flow. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z In transformers of the ordinary type it will be found that the wave of electromotive force of the secondary very nearly coincides with that of the primary, being, however, in opposite sign. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z The contact is made between the mercury and the steel by the electric wave generating an electromotive force in the aerial, sufficient to break through the thin film of oil. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The battery has a low electromotive force, about 0.7 of a volt, but as the internal resistance is also very low, quite a large current can be drawn from the cell. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z The electromotive energy called into action in these dry piles is less than that excited in the moist or hydro-electric piles, principally on account of the imperfect conduction of the paper. A Treatise on Meteorological Instruments Explanatory of Their Scientific Principles, Method of Construction, and Practical Utility 2011-06-19T02:00:15.717Z But this electromotive force, which is proportional to the current in the coil, is equal to the product of the resistance of the wire and the same current, or a known fraction of it. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z Generally the conditions are so adjusted that the electromotive force used in each of the motor circuits is that which is required to operate the motor when its circuits are in series. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z The working battery employed with it must only have an electromotive force of about a tenth of a volt. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The practical electrician has to measure electrical resistance, electromotive forces, and the capacities of condensers. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z The electromotive force, or E.M.F., is measured in terms of the work done in carrying unit quantity of electricity once round the circuit. The New Gresham Encyclopedia Volume 4, Part 2: Ebert to Estremadura 2011-04-14T02:00:56.200Z The magneto-electric machine imagined in the former paper gave a means of estimating the electromotive force of a cell or battery in absolute units. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z The electromotive force was regulated by means of an adjustable condenser within very wide limits, the limits being the greater, the greater the speed. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z This action, by varying the magnetic flux through the secondary coil, creates in it an electromotive force which causes a sound to be heard in the telephone connected to it. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Magnetomotive Force.—This is a force similar to electromotive force, that is, magnetic pressure. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z The electromotive force due to chemical action depends on the material of the electrodes and the nature of the electrolyte, and also to a slight extent on the temperature. The New Gresham Encyclopedia Volume 4, Part 2: Ebert to Estremadura 2011-04-14T02:00:56.200Z Thus the theory is only applicable when the electromotive force is not affected by variation of temperature. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z As this time is greater than half the period, it occurs that an opposing electromotive force begins to act while the current is still flowing. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z The demagnetisation of the iron which ensues produces an electromotive force in the secondary coil and causes a deflection of the galvanometer, and this deflection will continue and remain steady if the oscillation persists. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z A dynamo is a machine for filling and emptying conducting loops with magnetic flux, and utilizing the electromotive force thus induced in them for the production of current in the external circuit. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z When an electromotive force is applied, it causes a drift of the electrons in the opposite direction to the force, the charge on the electrons being negative. The New Gresham Encyclopedia Volume 4, Part 2: Ebert to Estremadura 2011-04-14T02:00:56.200Z Thus the electromotive force of the disk was opposed by a back electromotive force θε due to the chemical action in the voltameter or battery, to which the wires from the disk were connected. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z Unfortunately, the type of machine in which these conditions may be satisfied is of little practical value, owing to the small electromotive force obtainable and the difficulties in taking off the current. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z We have already seen that the receiving aerial has an alternating electromotive force set up in it by the impact of the successive electric waves sent out from the transmitter. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z What may be said of the electromotive force during the second half of the revolution? Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z Thus the electromotive force is equal to the change of this free energy per electrochemical equivalent of reaction in the cell. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z From this result Thomson proceeded to calculate the electromotive forces required to effect chemical changes of different kinds, and those of various types of voltaic cell. Lord Kelvin An account of his scientific life and work 2012-04-06T02:00:32.097Z To produce discharges in tubes devoid of electrodes was, however, not easy to accomplish, for the only available means of producing an electromotive force in the discharge circuit was by electro-magnetic induction. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z Supposing, therefore, that we connect to the oscillating circuit of the jar a number of bobbins having different time periods of oscillation, like organ-pipes, and supply them all with one common alternating electromotive force. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z From 0° to 90°, the electromotive force increases from 0 to maximum;2. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z Owing to the confusion introduced by the employment of the term force, Maxwell and other writers sometimes use the words electromotive intensity instead of electric force. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z Helmholtz takes the case of a circuit of resistance R in which acts an electromotive force due to a battery or thermopile. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z On the terminals of the condenser the electromotive force was about 120 volts, and from there inch by inch it gradually fell until at the terminals of the machine it was about 65 volts. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z A very violent electromotive force will cause them all to respond to some slight extent, no matter whether the period of that impluse is tuned to their common period precisely or not. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z From 90° to 180°, the electromotive force decreases from maximum to zero;3. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z M.H. von Jacobi showed that for a given electromotive force in the battery the horse-power is greatest when the current is reduced to one-half of what it would be if the engine were at rest. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z To find the current in each conductor when the individual resistances and electromotive forces are given, proceed as follows:—Consider any one mesh. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z If the capacity was increased or diminished, the electromotive force fell as expected. The inventions, researches and writings of Nikola Tesla With special reference to his work in polyphase currents and high potential lighting 2012-03-28T02:00:22.660Z In other words, if the tube is acted upon by a sufficient electromotive force, it is not necessary that electromotive force should be repeated at intervals to make this particular form of kumascope responsive. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z At this instant the electromotive force is zero, hence the sine curve as shown begins at E, the zero point—that is, on the axis or line of no pressure. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z In this condition there is complete electrical insulation between the jets, as may be proved by the inclusion in the circuit of a delicate galvanometer, and a low electromotive force. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3 "Capefigue" to "Carneades" Thus, as long as every ion of the solution is present in the layer of liquid next the electrode, the one which responds to the least electromotive force will alone be set free. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z By altering the distance between the plates until CD just begins to lose a negative charge, we find the velocity of the negative ion under unit electromotive intensity. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" All the detectors of the coherer type really depend for their actuation upon electromotive force; that is to say, upon the application to the terminals of the detector of a certain electromotive force. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z This increase is indicated by the gradual rise of the sine curve from E to F. The loop has now made one quarter of a revolution and the electromotive force reached its maximum value. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z The tension of the surface of contact of mercury and dilute sulphuric acid depends on the electromotive force acting between the mercury and the acid. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3 "Capefigue" to "Carneades" The electromotive force in the circuit is small, and there is large polarization in the circuit with only a small current. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z When this is the case the back electromotive force is destroyed and the same potential difference will carry a much larger current. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" The speed of the motor can be regulated by a small resistance, and can be adapted to the electromotive force used in the primary circuit. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z This is easily done, as the resultant electromotive force induced at any point in the revolution of the armature is equal to the sum of the pressures induced in AA′ and BB′. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z If the electromotive force is from the acid to the mercury the surface-tension increases; if it is from the mercury to the acid, it diminishes. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3 "Capefigue" to "Carneades" The concentration is known, and the conductivity can be measured experimentally; thus the average velocity with which the ions move past each other under the existent electromotive force can be estimated. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z For let E0 be the electromotive force of the battery, R the resistance of the leads, i the current, the potential difference between the terms in the gas will be E0 − Ri. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" The Wehnelt break does not increase the actual secondary electromotive force, nor apparently its duration, but it greatly increases the number of times per second this electromotive force makes it appearance. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Its magnetic field is obtained from permanent magnets, hence the electromotive force generated is comparatively small. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z G. Lippmann, who has made a careful investigation of the subject, finds that exceedingly small variations of the electromotive force produce sensible changes in the surface-tension. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3 "Capefigue" to "Carneades" It can be experimentally shown that a current cannot be created instantaneously in a circuit by any finite electromotive force, and that when once created it cannot be annihilated instantaneously. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z If the electromotive force is increased, in the case of a large number of ordinary dielectrics the apparent resistance at the end of one minute’s electrification decreases as the electromotive force increases. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" Hence this break increases the current, but not the electromotive force in the secondary coil. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The electromotive force is about 1.48 volts and the internal resistance about 4 ohms. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z The simplest experimental method of directly determining chemical affinity consists in the measurement of electromotive force. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Cavendish meant by the term “velocity” what we now call the current, and by “resistance” the electromotive force which maintains the current. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z In metallic conduction it is found that the current is proportional to the applied electromotive force—a relation known by the name of Ohm’s law. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" It, therefore, does not assist us in the direction required—viz., in prolonging the duration of the secondary electromotive force to enable larger capacities to be charged. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Bichromate cells give a strong current, the electromotive force of a single cell being 2 volts. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z We do this by measuring the electron-moving-force or “electromotive force” which each battery can exert. Letters of a Radio-Engineer to His Son This result thus obtained by Cavendish in January 1781, that the current varies in direct proportion to the electromotive force, was really an anticipation of the fundamental law of electric flow, discovered independently by G.S. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Ohm’s law states that the current C is proportional to the electromotive force E, or C = kR, where k is a constant called the conductivity of the circuit. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" Both of these operations result in the creation of an alternating electromotive force in the receiving aerial wire. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Its electromotive force is from 1.9 to 2 volts, and the 6 in. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z They defined it by telling how to make a particular kind of battery and then saying that this battery had an electromotive force of a certain number of volts. Letters of a Radio-Engineer to His Son At the time when Maxwell developed his theory the dielectric constants of only a few transparent insulators were known and these were for the most part measured with steady or unidirectional electromotive force. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Both effects thus involve internal electromotive forces, and prevent the application of Ohm’s law to the electrolytic cell as a whole. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" One problem in connection with the design of a receiving aerial is that of increasing its effective length and capacity so as to increase correspondingly the electromotive force or current oscillations in it. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The absence of the porous pot decreases the internal resistance, but the electromotive force is the same as in the ordinary type of Daniell cell. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z To express electromotive force and give the results of our measurements we must have some unit. Letters of a Radio-Engineer to His Son Only when the applied electromotive force exceeds this reverse force of polarization, will a permanent steady current pass through the liquid, and visible chemical decomposition proceed. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z If the current be stopped before such a film is completed, the reverse electromotive force is less than its full value. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" The committee appointed to test experimentally Ohm's law, that with any conductor the electromotive force is proportioned to the current produced, reports that this law is absolutely correct. The Galaxy Vol. 23, No. 1 Ohm’s law states that the strength of a current due to an electromotive force falls off in proportion as the resistance in the circuit increases. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z They are not good for ordinary purposes because the moment they go to work driving electrons the conditions inside them change so their electromotive force is changed. Letters of a Radio-Engineer to His Son It seems that this reverse electromotive force of polarization is due to the deposit on the electrodes of minute quantities of the products of chemical decomposition. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z The currents from the secondary circuit of a small induction coil are satisfactory, or the currents of an alternating electric light supply may be transformed down to an electromotive force of one or two volts. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" That electromotive force acting on a dielectric produces what we call electric displacement. The World's Greatest Books — Volume 15 — Science By joining in series a number of conductors or coils moving in a magnetic field, the electromotive forces in the separate parts are added together. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z If the batteries are equal in electromotive force these electrons will stay right where they are. Letters of a Radio-Engineer to His Son Differences between the two electrodes are thus set up, and, as we have seen above, an electromotive force will therefore exist between them. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Direct currents of somewhat high electromotive force are used to work the bridge. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" If we wish our current to leap over five intervals, and produce five lights in succession, we must invoke a sufficient electromotive force. Fragments of science, V. 1-2 The more rapid the motion, the higher will be the induced electromotive force. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z An ampere is an electromotive force of one volt through a resistance of one ohm. Electricity for Boys The opposing force of polarization is about 1.7 volt, but, when the plates are disconnected and used as a source of current, the electromotive force they give is only about 1.07 volt. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z A narrow glass tube is fixed horizontally into side openings in two glass vessels, and an electric current passed through it by means of platinum electrodes and a battery of considerable electromotive force. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" In the machines intended for the production of the electric light, the electromotive force is so great as to permit of the introduction of several lights in the same circuit. Fragments of science, V. 1-2 From 180° to 270°, current reverses and the electromotive force increases from zero to maximum;4. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z In practice the word "current" is used to designate ampere flow; and electromotive force, or E. M. F., is used instead of voltage. Electricity for Boys Let an electromotive force exactly equal to that of the cell be applied to it in the reverse direction. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Now, Ohm’s Law implies that no work is done by the current in overcoming reversible electromotive forces such as those of polarization. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" He demonstrated that, above and below a certain range of electromotive intensity, the polar effects of currents are precisely opposite to those enunciated by Pfluger. Sir Jagadis Chunder Bose His Life and Speeches It was stated that, during the revolution of the loop, the magnetic lines were cut “with increasing or decreasing rapidity,” causing the electromotive force to rise or fall. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z The variable known weights are units separate from the scales, but the potentiometer provides its own variable known electromotive force. The Working of Steel Annealing, Heat Treating and Hardening of Carbon and Alloy Steel The result is that a high electromotive force is set up, which has been calculated as 0.52 volt, and observed as 0.51 volt. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Under the influence of an electromotive force the barium ions moved up the tube, disclosing their presence by the trace of insoluble barium sulphate formed. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" Considerations showing that electric response is due to molecular disturbance.—The electromotive variation varies with the substance. Response in the Living and Non-Living In like manner other points are obtained, and the curved line through them will represent the variation in the electromotive force for all points of the revolution. Hawkins Electrical Guide, Number One Questions, Answers, & Illustrations, A Progressive Course of Study for Engineers, Electricians, Students and Those Desiring to acquire a Working Knowledge of Electricity and its Applications 2011-12-24T03:07:54.823Z This electromotive force, or voltage, may be measured, and, from a chart previously prepared, the temperature determined. The Working of Steel Annealing, Heat Treating and Hardening of Carbon and Alloy Steel The conductivity gives us the amount of electricity conveyed per second under a definite electromotive force. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z The one most frequently employed is to find the electromotive intensity required to force an ion against the stream of gas moving with a known velocity parallel to the lines of electric force. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" The intensity of the response, however, does not depend on the chemical activity of the substance, for the electromotive variation in the relatively chemically inactive tin is greater than that of zinc. Response in the Living and Non-Living These electromotive forces cause what are known as "eddy currents." The Report on Unidentified Flying Objects With this crude apparatus and with no greater electromotive force than could be attained from a voltaic pile, he converted charcoal into graphite, volatilized phosphorus from its compounds, isolated metallic calcium and synthesized calcium carbide. Creative Chemistry Descriptive of Recent Achievements in the Chemical Industries These phenomena are explained by the existence of a reverse electromotive force at the surface of the platinum plates. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z If R + dE/di is positive there will be an unbalanced electromotive force round the circuit tending to stop the current. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" We must not forget that even insulators, as well as conductors, cutting lines of force, have the electromotive force developed in them. Scientific American Supplement, No. 711, August 17, 1889 The furnace at present in use is charged in substantially the same manner, and the current is supplied by a Brush machine of variable electromotive force driven by an equivalent of forty horse power. Scientific American Supplement, No. 508, September 26, 1885 Magnesium in particular, also zinc and cadmium, were greatly depressed in electromotive force in electrolytes by elevation of temperature. Scientific American Supplement, No. 443, June 28, 1884 Since zinc goes into solution and copper comes out, the electromotive force of the cell will be the difference between the two effects. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z If, however, R + dE/di is negative there will be an unbalanced electromotive force tending to increase the current still further; thus the current will go on increasing and the condition will be unstable. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" Here it may be so effective that the form of the curve is completely lost unless a very large electromotive force is used to separate the ions when the ionisation is being investigated. The Birth-Time of the World and Other Scientific Essays With a high resistance in the outside circuit, the deflections of the ammeter will be small, but such as they are, they will fairly accurately represent the electromotive forces which produce them. General Science But when you come to run twenty or thirty or fifty cars on one line, you will require very large conductors or dangerously high electromotive force. Scientific American Supplement, No. 620, November 19,1887 W. Nernst, to whom this theory is due, determined the electromotive force of this cell experimentally, and found the value 0.055 volt. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z If we keep the external electromotive force the same and gradually increase the resistance in the leads, the line LM will become steeper and steeper. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" Its electromotive force is very nearly one volt. Scientific American Supplement, No. 421, January 26, 1884 The unit of electromotive force is called the volt. General Science The current required to run a street car is about thirty amperes, and an electromotive force of about 180 volts. Scientific American Supplement, No. 620, November 19,1887 By both these methods the single potential-differences found at the surfaces of the zinc and copper have opposite signs, and the effective electromotive force of a Daniell’s cell is the sum of the two effects. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z This resistance is thrown in or out by means of a motor device actuated by an electromotive force indicator. Scientific American Supplement, No. 623, December 10, 1887 A battery of an arbitrary electromotive force, E, actuates at the same time the two antagonistic circuits of a differential galvanometer. Scientific American Supplement, No. 613, October 1, 1887 The strength of a steady current depends upon these two factors only, the electromotive force which causes it and the resistance which it has to overcome. General Science Dr. G. Gore, F.R.S., has invented an improved thermopile for measuring small electromotive forces. Scientific American Supplement, No. 441, June 14, 1884. It must be remembered, however, that variations in conditions modify the electromotive force required for any given process. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z There are several devices by which it has been found possible to enable a dynamo to maintain a constant electromotive force, even if the speed of rotation varies over considerable limits. Scientific American Supplement, No. 623, December 10, 1887 To utilize it, would require that the vibrations of the diaphragm cause the electromotive force of a battery or machine to vary in harmony with the sound waves. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The power that causes the current is called the electromotive force, and the value of the electromotive force, generally written E.M.F., of a cell depends upon the materials used. General Science On having been verified with a standard voltaic cell the apparatus becomes itself a standard, especially for small electromotive forces. Scientific American Supplement, No. 441, June 14, 1884. During a small electric transfer through the cell, the external work done is Ee, where E is the electromotive force. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Accordingly, within certain limits, the electromotive force of the dynamo is independent of the speed of rotation. Scientific American Supplement, No. 623, December 10, 1887 This disturbance of the flux creates electromotive forces in those windings. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. When the cell consists of copper, zinc, and dilute sulphuric acid, the electromotive force has a definite value which is always the same no matter what the size or shape of the cell. General Science For higher electromotive forces than a volt, several of these piles would have to be connected in series. Scientific American Supplement, No. 441, June 14, 1884. As stated above, an electromotive force is set up whenever there is a difference of any kind at two electrodes immersed in electrolytes. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z The electromotive force of this secondary current is somewhat higher than is necessary. Scientific American Supplement, No. 623, December 10, 1887 The inductance of a circuit is one henry when a change of one ampere per second produces an electromotive force of one volt. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Each combination of material has its own specific electromotive force. General Science The fractional electromotive force is obtained by means of a sliding contact which cuts out so many pairs as is required. Scientific American Supplement, No. 441, June 14, 1884. With the scale at a distance of two metres, a deflection of 130 mm. was produced by an electromotive force of 0.1 volt. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Electrical Governor—A new apparatus for preserving a constant electromotive force with varying dynamo speed—1 illustration. Scientific American Supplement, No. 623, December 10, 1887 Inductance is the property of a circuit by which change of current in it tends to produce in itself and other conductors an electromotive force other than that which causes the current. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The electromotive force of one cell may not give a current strong enough to ring a door bell or to operate a telephone. General Science It results from this that as soon as we propose to obtain an electromotive force, however slight it be, we must get it with machines of large dimensions. Scientific American Supplement, No. 441, June 14, 1884. This solution, being an inferior conductor of electricity, requires a much higher electromotive force to drive the current through it, and is therefore more costly in use. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Equation 2 shows that with a given load the speed depends upon E, the electromotive force of the main, and R the resistance in circuit. Scientific American Supplement, No. 388, June 9, 1883 The units are: of current, the ampere; of electromotive force, the volt; of resistance, the ohm. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Since electromotive force, or voltage, is the cause of current, it should be possible to compare different electromotive forces by comparing the currents which they produce in a given circuit. General Science Then the charged positive ions travel in the direction of the electromotive force and the negative ions in the opposite direction. The New Physics and Its Evolution In settling the electromotive force of the dynamo to be employed, attention must be paid to the question of charging secondary cells, if these are used. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z To produce discharges in tubes devoid of electrodes was, however, not easy to accomplish, for the only available means of producing an electromotive force in the discharge circuit was by electromagnetic induction. Scientific American Supplement, No. 810, July 11, 1891 Similarly, a variation of the electromotive forces in the windings varies the pull of the permanent magnet of the receiving instrument upon its diaphragm. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Suppose the line and electromagnet have together a resistance of 6 ohms, and that we have 24 small Daniell cells, each of electromotive force say 1 volt, and of internal resistance 4 ohms. Scientific American Supplement, No. 787, January 31, 1891 When a condenser is put on a dynamo, the condenser current leads relatively to the electromotive force, and therefore strengthens the field magnets and increases the pressure. Scientific American Supplement, No. 795, March 28, 1891 The electromotive force of these cells varies between 2.2 and 1.8 volts as they discharge; hence the above number of cells is sufficient for maintaining the necessary electromotive force. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z By this change the resistance is considerably diminished, the electromotive force rises to 2.40 volts, the return is greater, the output more constant, and the weight is considerably reduced. Scientific American Supplement, No. 530, February 27, 1886 This, by the laws of electromagnetic induction, will produce corresponding electromotive forces in the secondary winding and, therefore, corresponding currents in that winding if its circuit be closed. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The electromagnetic inertia, or self-inductive property of the electric circuit, causes the currents to rise and fall later in time than the electromotive forces by which they are occasioned. Scientific American Supplement, No. 787, January 31, 1891 Mr. Kapp's experiment was not conclusive, for the length of spark is not an accurate measure of electromotive force. Scientific American Supplement, No. 795, March 28, 1891 In working such a plant it is necessary to have the means of varying the electromotive force of the dynamo as the charging of the cells proceeds. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z During the period of charging the accumulators, the intensity of the current and the electromotive force was measured every quarter of an hour, and thence the energy stored up in the battery was deduced. Scientific American Supplement, No. 530, February 27, 1886 It is called magnetomotive force and is analogous to electromotive force, that is, the force which tends to drive an electric current through a circuit. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. This current is continuous, constant, and of considerable electromotive force. Scientific American Supplement, No. 492, June 6, 1885 According to Ohm's law, the strength of current is proportional to the electromotive force divided by the total resistance, external and internal. Scientific American Supplement, No. 481, March 21, 1885 The cell, together with this balancing electromotive force, is thus a reversible system in true equilibrium, and the thermodynamical reasoning applicable to such systems can be used to examine its properties. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Every one knows that the Latimer-Clark element is now the best standard of electromotive force; but let us not forget that this is on condition of its being employed in open circuit. Scientific American Supplement, No. 598, June 18, 1887 The electromotive force and the current will, therefore, be zero at this time. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Later, as was shown in the previous paper by the present writer Volta came to regard the metallic contact as the cause of the electromotive force. Popular Science Monthly Oct, Nov, Dec, 1915 — Volume 86 The electromotive force and resistance is constant if the velocity is constant. Scientific American Supplement, No. 481, March 21, 1885 It is now evident that the electromotive force of an ordinary chemical cell such as that of Daniell depends on the concentration of the solutions as well as on the nature of the metals. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z There was nothing I could find bearing upon the counter electromotive force of the armature, and the effect of the resistance of the armature on the work given out by the armature. Edison, His Life and Inventions In other words, the polarization gradually gains on the preventive means and so gradually reduces the current by increasing the resistance of the cell and lowering its electromotive force. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. After some ``forming'' operations described below, he obtained a cell having a high electromotive force, a low resistance, a large capacity and almost perfect freedom from polarization. The Project Gutenberg Encyclopedia Volume 1 of 28 The electromotive force is independent of the velocity, but diminishes as the moisture increases, and is about equal to 52,000 Daniell cells. Scientific American Supplement, No. 481, March 21, 1885 Once more we see that it is the total impending change in the available energy of the system which controls the electromotive force. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z These are deposited in succession, and are sharply separated if the electromotive power is not too great. Scientific American Supplement, No. 433, April 19, 1884 Its compactness and portability and its freedom from local action make it particularly adaptable to use in portable testing outfits where constant electromotive force and very small currents are required. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The influence of diffusion on the electromotive force is illustrated by fig. The Project Gutenberg Encyclopedia Volume 1 of 28 The battery has rather greater electromotive force when this regenerated lye is used, because certain foreign matters from the carbon, like sulphur, chlorine, sulphuric acid, etc., are removed by this treatment. Scientific American Supplement, No. 392, July 7, 1883 This drop in the electromotive force has led to the belief that the cell is not reversible. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z According to the committee of Parliament investigation, the electromotive force dangerous to life is about 300 volts; this then is the quantity, E, in the formula. Scientific American Supplement, No. 433, April 19, 1884 At this point, therefore, the electromotive force and the current will be a maximum. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. If the discharge be complete the recuperation refers only to the electromotive force; the pressure falls at once on closed circuit. The Project Gutenberg Encyclopedia Volume 1 of 28 Launches.—A paper read before the Society of Arts by A. RECKENZAUN, and discussion on the same.—Advantages of electromotive power.— Scientific American Supplement, No. 430, March 29, 1884 If secondary effects are eliminated, the deposition of metals also is a reversible process; the decomposition voltage is equal to the electromotive force which the metal itself gives when going into solution. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z This means, therefore, that when the electromotive force or potential is great enough to send a current of 1/33 ampere through the body, fatal results will ensue. Scientific American Supplement, No. 433, April 19, 1884 At this point, therefore, the electromotive force and the current in the loop again will be zero. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Now this machine, which may be called the motor, produces a back electromotive force, and the mechanical power given out is proportional to the back electromotive force multiplied into the current. Scientific American Supplement, No. 288, July 9, 1881 The electromotive force of such a cell is 1.03 volts, and a current equivalent to one volt passing through a resistance of one ohm was found to decompose 0.00146 grain of water in one second. Scientific American Supplement, No. 275, April 9, 1881 This reverse electromotive force of polarization is produced in all electrolytes when the passage of the current changes the nature of the electrodes. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Here every additional lamp added to the circuit means an increase in resistance, and consequent increase in electromotive force or potential. Scientific American Supplement, No. 433, April 19, 1884 The amount of electromotive force, that is generated between two dissimilar elements immersed in an electrolyte is different for different pairs of elements and for different electrolytes. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Hence the distances separating the equipotential surfaces are a measure of the electromotive force present. Scientific American Supplement, No. 288, July 9, 1881 Rusty lead, so to speak, so connected with bright lead, has a high electromotive force. Steam, Steel and Electricity In each conductor a current may exist, and along each conductor there is a fall of potential, or an active electromotive force may be acting in it. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Taking for example a well known system of arc lighting, we find that the lamps require individually an electromotive force of 40 volts with a current of 10 amperes. Scientific American Supplement, No. 433, April 19, 1884 They give a relatively high electromotive force and have a moderately low internal resistance, so that they are capable of giving rather large currents for short intervals of time. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. If there are a number of generators of electricity in a circuit, whose electromotive forces in volts are E_1, E_2, etc., and if there are also opposing electro-motive forces. Scientific American Supplement, No. 288, July 9, 1881 A fish, exhausted by too numerous electrical discharges, suffered much more than another fish deprived, by dividing the nerves, of any communication between the brain and the electromotive apparatus. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 When the applied electromotive force is diminished by an infinitesimal amount, the cell produces a current in the usual direction, and the ordinary chemical changes occur. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z It has been found that two cells having an electromotive force of about two volts each will in this process suffice; if preferred, however, a very small dynamo machine can be used. Scientific American Supplement, No. 433, April 19, 1884 This type of cell has an electromotive force of about 1.55 volts and recuperates very quickly after severe use. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The difference of potential between any two points is called an electromotive force. Scientific American Supplement, No. 288, July 9, 1881 Free.—When a condenser discharges through an oscillation circuit, where there is no outside electromotive force acting on it, the oscillations are said to be free. The Radio Amateur's Hand Book For cells in which the electromotive force varies with temperature, the full equation given by Gibbs and Helmholtz has also been confirmed experimentally. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z There is a limit of electromotive force below which the indicator fails to give reliable readings. Scientific American Supplement, No. 433, April 19, 1884 There is, therefore, actual reduction in the electromotive force of the cell, as well as an increase in internal resistance. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Its electromotive force is determined by the distance in the series between the metals used. Man or Matter HENRY.—The inductance in a circuit in which the electromotive force induced is 1 volt when the inducing current varies at the rate of 1 ampere per second. The Radio Amateur's Hand Book The electromotive force is practically constant no matter what the velocity of the disks, but according to some observers the internal resistance decreases as the velocity increases. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z At this end of the line I merely measure the electromotive force developed by the difference in temperature of two similar thermo- electric junctions, opposed. The Dream Doctor The electromotive force of this cell when new is about 1.47 volts. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The difference of electrical condition or "potential" between the plates by which the current is started has been called the electromotive force, or force which puts the electricity in motion. The Story of Electricity The volt is the electromotive force which produces a current of 1 ampere when steadily applied to a conductor the resistance of which is 1 ohm. The Radio Amateur's Hand Book Volta then proved that all metals could be arranged in an electromotive series such that each became positive when placed in contact with the one next below it in the series. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z When the electromotive force begins to fall, the condenser can no longer retain Page 185 its charge and a current will, therefore, flow out of it. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. This cell gives an electromotive force of 2.1 volts and a very large current when it is in good condition, since its internal resistance is low. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. This arrangement multiplies alike the electromotive force and the resistance. The Story of Electricity The henry is the inductance in a circuit in which the electromotive force induced is 1 volt when the inducing current varies at the rate of 1 ampere per second. The Radio Amateur's Hand Book The origin of the electromotive force in the pile has been much discussed, and Volta’s discoveries gave rise to one of the historic controversies of science. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z When the electromotive force reaches its maximum, the condenser will have received its full charge for that potential, and the current flow into it will cease. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. This current is caused by an effective electromotive force which may be as great as 100 volts, produced immediately by the energy of the user. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The electromotive force of the battery is the sum of the electromotive forces of all the cells, and the resistance of the battery is the sum of the resistances of all the cells. The Story of Electricity OHM'S LAW.—The important fixed relation between the electric current, its electromotive force and the resistance of the conductor in which it flows. The Radio Amateur's Hand Book The sensitiveness of the coherer depends on the electromotive force put in the galvanometer circuit. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z The electric pressure is greater the more the difference of potential or electromotive force. The Story of Electricity The electromotive force induced by the capacity of a line leads the impressed electromotive force by 90 degrees. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. High electromotive forces or "pressures" capable of overcoming high resistances outside the battery can be obtained in this way. The Story of Electricity VOLT.—The electromotive force which produces a current of 1 ampere when steadily applied to a conductor the resistance of which is one ohm. The Radio Amateur's Hand Book The relation between these is expressed by the well-known law of Ohm, which runs: A current of electricity is directly proportional to the electromotive force and inversely proportional to the resistance of the circuit. The Story of Electricity Obviously the higher the electromotive force and the lower the resistance, the stronger will be the current in the conductor. The Story of Electricity The inductive electromotive force lags 90 degrees behind the impressed electromotive force. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. This arrangement does not increase the electromotive force, but diminishes the resistance. The Story of Electricity Hence it is desirable to have a cell which will give a high electromotive force and a low internal resistance. The Story of Electricity The Latimer Clark "standard" cell is used by electricians in testing, as a constant electromotive force. The Story of Electricity The electromotive force and current of a thermo-electric couple is very much smaller than that given by an ordinary voltaic cell. The Story of Electricity The formula of this relation, Ohm's law, is C = E ÷ R C being the current which results from E, the electromotive force, acting upon R, the resistance. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. In alternate current machines the electromotive force keeps constant, as the field- magnets are excited by a separate machine, giving a continuous current. The Story of Electricity The resistance of such a filament hot is about 200 ohms, and to produce a good light from it the battery or dynamo ought to give an electromotive force of at least 100 volts. The Story of Electricity The electromotive force of a Clark standard cell at a temperature of 15 degrees centigrade is 1.434 volts. The Story of Electricity The volt is equal to a hundred million, 10^8, C. G. S. units of electromotive force. The Story of Electricity When the connection between the plates and the battery is made, the two plates become charged to a difference of potential equal to the electromotive force of the battery. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. So, too, electricity flows by the electromotive force from a place of higher to a place of lower electric level or potential. The Story of Electricity For example, if we know the electromotive force or difference of potential in volts and the resistance in ohms of an electric circuit, we can easily find the current in amperes. The Story of Electricity |
| 随便看 |
英语例句辞典收录了117811条英语例句在线翻译词条，基本涵盖了全部常用单词及词组的例句翻译及用法，是英语学习的有利工具。