| 单词 | inductance |
| 例句 | The answer is yes, and that physical quantity is called inductance. College Physics for AP Courses 2015-08-12T00:00:00Z Unfortunately, because the inductance of such devices is proportional to their cross-sectional area, it is difficult to miniaturize them while keeping a reasonably high inductance. Inductors enter the world of quantum mechanics 2020-10-06T04:00:00Z He soon showed that by distributing the line's inductance uniformly, it was possible to diminish both the signal's attenuation and its distortion. Engineering: Reclusive genius who connected the world : Nature : Nature Research 2017-09-12T04:00:00Z Apparatus for showing Stationary Waves in long Solenoid A. I, induction coil; S, spark gap; L, inductance coil; C1C2, Leyden jars; E, earth wire. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The plate circuit of the second tube is connected to the plate of the detector tube through both capacity and inductance.” The Radio Boys at Mountain Pass The Midnight Call for Assistance 2012-01-02T03:00:17.697Z Mutual inductance is the effect of Faraday’s law of induction for one device upon another, such as the primary coil in transmitting energy to the secondary in a transformer. College Physics for AP Courses 2015-08-12T00:00:00Z More spectacularly, it was predicted that this field would generate an inductance that is proportional to the rate of change of the current density. Inductors enter the world of quantum mechanics 2020-10-06T04:00:00Z In the latter there are almost insuperable obstacles caused by the capacity and inductance of the circuit, while in the wireless method there is very little difficulty. Marvels of Scientific Invention An Interesting Account in Non-technical Language of the Invention of Guns, Torpedoes, Submarine Mines, Up-to-date Smelting, Freezing, Colour Photography, and many other recent Discoveries of Science 2011-11-19T03:00:24.517Z This high frequency can only be obtained either by greatly reducing the inductance of the primary discharge circuit, or reducing the capacity. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Inductance.—As soon as we turn our attention, however, to alternating or periodic currents we find ourselves compelled to take into account another quality of the circuit, called its “inductance.” Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z The larger the mutual inductance M , the more effective the coupling. College Physics for AP Courses 2015-08-12T00:00:00Z The authors investigated the emergent inductance of their inductor using a technique called lock-in detection. Inductors enter the world of quantum mechanics 2020-10-06T04:00:00Z This is called "inductance," and it has exactly the same effect upon the current that inertia has upon a body. Marvels of Scientific Invention An Interesting Account in Non-technical Language of the Invention of Guns, Torpedoes, Submarine Mines, Up-to-date Smelting, Freezing, Colour Photography, and many other recent Discoveries of Science 2011-11-19T03:00:24.517Z The primary circuit, if formed of 360 turns of No. 12 H.C. copper wire, would have a resistance of 0�36 of an ohm, and an inductance of 0�02 of a henry. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z If a conductor of capacity C has its terminals connected by a wire of resistance R and inductance L, it becomes important to consider 215 the subsequent motion of electricity in the wire. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z One way to reduce mutual inductance M is to counterwind coils to cancel the magnetic field produced. College Physics for AP Courses 2015-08-12T00:00:00Z By changing the spin-structure state of the device, the authors clarified the correspondence between the emergent inductance and the non-collinearity and dynamics of the spin structures. Inductors enter the world of quantum mechanics 2020-10-06T04:00:00Z What inertia is to a material body inductance is to an electric current. Marvels of Scientific Invention An Interesting Account in Non-technical Language of the Invention of Guns, Torpedoes, Submarine Mines, Up-to-date Smelting, Freezing, Colour Photography, and many other recent Discoveries of Science 2011-11-19T03:00:24.517Z The short circuiting of the secondary circuit almost entirely annuls the inductance of the primary circuit. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Neumann founded a mathematical theory of induced currents, discovering a quantity M, called the “potential of one circuit on another,” or generally their “coefficient of mutual inductance.” Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Figure 23.40 The heating coils of an electric clothes dryer can be counter-wound so that their magnetic fields cancel one another, greatly reducing the mutual inductance with the case of the dryer. College Physics for AP Courses 2015-08-12T00:00:00Z This correspondence is well explained by the previously mentioned mechanism for emergent inductance. Inductors enter the world of quantum mechanics 2020-10-06T04:00:00Z There is capacity at each end and a fairly long length of wire to provide the inductance. Marvels of Scientific Invention An Interesting Account in Non-technical Language of the Invention of Guns, Torpedoes, Submarine Mines, Up-to-date Smelting, Freezing, Colour Photography, and many other recent Discoveries of Science 2011-11-19T03:00:24.517Z The chief difficulty we have to contend against in the construction of an effective oscillation transformer is the inductance of the primary circuit and the magnetic leakage that takes place. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z He added definiteness to the idea of the self-induction or inductance of an electric circuit, and gave a mathematical expression for the current flowing out of a Leyden jar during its discharge. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" 2011-01-29T03:00:23.777Z Let us use this last equation to find an expression for the inductance of a solenoid. College Physics for AP Courses 2015-08-12T00:00:00Z For example, Yokouchi and colleagues discovered that the current-driven dynamics of the helical spin structures are responsible for the large emergent inductance. Inductors enter the world of quantum mechanics 2020-10-06T04:00:00Z That frequency depends upon the two electrical properties of the circuit: capacity and inductance. Marvels of Scientific Invention An Interesting Account in Non-technical Language of the Invention of Guns, Torpedoes, Submarine Mines, Up-to-date Smelting, Freezing, Colour Photography, and many other recent Discoveries of Science 2011-11-19T03:00:24.517Z In this case, a condenser and inductance are connected in series to the spark balls of an induction coil, and oscillations are set up in this circuit. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z In cases where absence of inductance in the instrument is important, e.g. in the measurements in wireless-telegraph and telephone circuits, the "hot-wire" ammeter is used. The New Gresham Encyclopedia. Vol. 1 Part 2 Amiel to Atrauli Note that the inductance depends only on the physical characteristics of the solenoid, consistent with its definition. College Physics for AP Courses 2015-08-12T00:00:00Z By contrast, the fan-shaped structures yield a much lower inductance because their local angular variations are much smaller than are those of the other structures. Inductors enter the world of quantum mechanics 2020-10-06T04:00:00Z The change, of course, is made by altering the capacity, or inductance, or both. Marvels of Scientific Invention An Interesting Account in Non-technical Language of the Invention of Guns, Torpedoes, Submarine Mines, Up-to-date Smelting, Freezing, Colour Photography, and many other recent Discoveries of Science 2011-11-19T03:00:24.517Z The dash is really a series of closely adjacent dots, which run together in virtue of the inertia and inductance of the different parts of the whole receiving apparatus. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The closed oscillatory circuit consists of an inductance F, spark-gap G, and a block condenser C. H is a spark-coil for supplying the energy, the secondary J being connected to the spark-gap. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 The body of the car increases the inductance and the circuit changes sending a signal to the traffic lights to change colors. College Physics for AP Courses 2015-08-12T00:00:00Z When the core is drawn out of the coil, its impedance is diminished because the inductance is diminished. Cyclopedia of Telephony and Telegraphy, Vol. 2 A General Reference Work on Telephony, etc. etc. The shunt consists of a wire leading from the copper to the carbon rod with a condenser and an inductance coil inserted in it. Marvels of Scientific Invention An Interesting Account in Non-technical Language of the Invention of Guns, Torpedoes, Submarine Mines, Up-to-date Smelting, Freezing, Colour Photography, and many other recent Discoveries of Science 2011-11-19T03:00:24.517Z Each of these bobbins has a certain electrical capacity with respect to the earth, when considered as an insulated conductor, and it has also a certain inductance. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z A is the aerial, E earth, T inductance, L ammeter. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 So in this text the inductance L is usually a given quantity. College Physics for AP Courses 2015-08-12T00:00:00Z This means that the best conditions exist when the resistance is low and the inductance large. Cyclopedia of Telephony and Telegraphy, Vol. 2 A General Reference Work on Telephony, etc. etc. In that now adopted the resistance wire is carefully insulated and wound on a brass cylinder, being doubled on itself to annul inductance as much as possible. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 8 "Conduction, Electric" We arrange also another closed oscillation circuit, consisting of two Leyden jars and a variable inductance coil and a pair of spark balls which are connected to an induction coil. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z A is the aerial; T, the inductance; E, earth; L, hot-wire ammeter. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 It is instructive to derive an equation for its inductance. College Physics for AP Courses 2015-08-12T00:00:00Z It takes time to get a full-sized stream going through a coil because of the inductance of the coil. Letters of a Radio-Engineer to His Son In his wireless installation, a network of insulated wires, suspended in the air above, is one plate, the earth is the other; and the two are connected by an inductance coil. The War in the Air; Vol. 1 The Part played in the Great War by the Royal Air Force In this manner we can set up oscillations in the discharge circuit of these Leyden jars, and we can vary the time period by altering the inductance and the capacity. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z UHF reception should be tried with and without the inductance wire to obtain the best overall results. Zenith Television Receiver Operating Manual One common application of inductance is used in traffic lights that can tell when vehicles are waiting at the intersection. College Physics for AP Courses 2015-08-12T00:00:00Z Therefore, if we make the inductance of the coil small, keeping the condenser the same, we shall make the time required for the current to start and stop smaller. Letters of a Radio-Engineer to His Son It behooves you to have fair inductance at court. The Panchronicon In making this adjustment of inductance, we are tuning, as it is called, the Leyden jar discharge circuit to the resonating bobbin. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The type of transmitter is a simple rotary gap, indirectly excited spark and provided with nine taps on the inductance coil of the closed oscillating circuit. The Radio Boys Trailing a Voice or, Solving a Wireless Mystery In an inductor, the magnetic field is directly proportional to current and to the inductance of the device. College Physics for AP Courses 2015-08-12T00:00:00Z One rule, then, for increasing the frequency of an audion oscillator is to decrease the inductance. Letters of a Radio-Engineer to His Son He could see coils of bare metal, and arrangements which might have been inductances. Long Ago, Far Away A very small variation of the inductance of the jar circuit causes the vacuum tube to change in luminosity. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The signal had been transferred by inductance in the wall wiring and amplified over the public-address system. Tom Swift and the Electronic Hydrolung Would you use a large inductance or a large capacitance in series with a system to filter out low frequencies, such as the 100 Hz hum in a sound system? College Physics for AP Courses 2015-08-12T00:00:00Z To decrease the frequency we can either increase the capacity or increase the inductance or do both. Letters of a Radio-Engineer to His Son The lamps are stabilized by resistance and inductance coils. Artificial Light Its Influence upon Civilization One end of this secondary circuit is attached to the aerial and the other end is connected to the earth through a variable inductance coil. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The impedance of a few turns of heavy wire may be negligible to alternating currents of ordinary frequencies because the resistance of the wire is low, its inductance small, and the frequency finite. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Does inductance depend on current, frequency, or both? College Physics for AP Courses 2015-08-12T00:00:00Z Decreasing the capacity would make the frequency higher, but increasing the inductance would make it lower. Letters of a Radio-Engineer to His Son Referring to Figure 1 let us examine first the construction of the receiving inductance marked L. The latter is shown in detail in Figure 2, and consists of a heavy piece of cardboard. The Radio Boys on the Mexican Border At the receiving end, the aerial is connected in series with a variable inductance and with the primary circuit of another oscillation transformer, the second terminal of which is connected to the earth. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z If the coil shown therein be considered an arrangement of conductors having inductance, it will be seen that a favorable place Page 300 for an air-gap arrester is between that impedance and the line. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The characteristic time τ depends on only two factors, the inductance L and the resistance R . College Physics for AP Courses 2015-08-12T00:00:00Z A coil of wire will have more inductance the more turns there are to it. Letters of a Radio-Engineer to His Son Both these causes tend to diminish the amount of current that flows, and the inductance also tends to delay the flow. Scientific American Supplement, No. 787, January 31, 1891 The terminals of the condenser which is inserted in the middle of the secondary circuit of the oscillation transformer are connected through two small inductance coils with a relay and a single cell. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Describe Professor Pupin's method of inserting inductance into the telephone line. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The greater the inductance L , the greater τ is, which makes sense since a large inductance is very effective in opposing change. College Physics for AP Courses 2015-08-12T00:00:00Z Electrons only influence other electrons which are in parallel paths. 103When we want a large inductance we wind the coil so that there are many parallel paths. Letters of a Radio-Engineer to His Son In all such cases the impedance which the circuit offers is made up of two things—resistance and inductance. Scientific American Supplement, No. 787, January 31, 1891 Accordingly, the inductance and capacity of the lateral branch of the transmitter is altered until the hot wire ammeter in the base of the aerial shows the largest possible current. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z 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. Mutual inductance is the effect of two devices in inducing emfs in each other. College Physics for AP Courses 2015-08-12T00:00:00Z If he did that he would have a coil without any inductance, that is, he would have only the natural inertia of the electrons to deal with. Letters of a Radio-Engineer to His Son In front of him was the transmitter joined to the metal box which contained the microphone, transformers and inductance tuning coil. The Boy Inventors' Radio Telephone I, induction coil; S, spark gap; A, aerial; CC, condensers; E, earth plate; R, relay; L, variable inductance; F, filings tube; B, battery. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Induction within a circuit occurs because the circuit possesses inductance; it is called self-induction. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Their mutual inductance M indicates the effectiveness of the coupling between them. College Physics for AP Courses 2015-08-12T00:00:00Z Then we have an inductance the value of which we can vary “step-by-step” in a convenient manner. Letters of a Radio-Engineer to His Son They added a tapped inductance in the aerial circuit of the transmitter and used variable capacitors instead of fixed ones. The Dawn of Amateur Radio in the U.K. and Greece: a personal view It should, therefore, be borne in mind in dealing with electrical oscillations that a condenser of sufficient capacity is practically a conductor, and an inductance coil of sufficient inductance is practically a non-conductor. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Compare this statement with the correlative generalization which follows the next thought upon inductance. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. A large mutual inductance M may or may not be desirable. College Physics for AP Courses 2015-08-12T00:00:00Z Another way to make a variable inductance is to make what is called a “variometer.” Letters of a Radio-Engineer to His Son Coupled Circuits.—Open and closed circuits connected together by inductance coils, condensers or resistances. The Radio Amateur's Hand Book Hence capacity and inductance are qualities of an electric circuit which are analogous to the elasticity and inertia of such a body as a heavy spring. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Capacity and inductance depend only on states of matter. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. We want a transformer to have a large mutual inductance. College Physics for AP Courses 2015-08-12T00:00:00Z There’s a case where their mutual relations, their mutual inductance, makes the job easier. Letters of a Radio-Engineer to His Son COUPLING, INDUCTIVE.—Oscillation circuits when connected together by inductance coils. The Radio Amateur's Hand Book The primary circuit or spark circuit has capacity—viz., the capacity of the energy-storing condenser—and it has also inductance—viz., the inductance of the primary circuit of the oscillation transformer. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Induction between circuits occurs because the circuits possess inductance; it is called mutual induction. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. But an appliance, such as an electric clothes dryer, can induce a dangerous emf on its case if the mutual inductance between its coils and the case is large. College Physics for AP Courses 2015-08-12T00:00:00Z Suppose you wind two inductance coils and connect them in series. Letters of a Radio-Engineer to His Son CAPACITY, DISTRIBUTED.—A coil of wire not only has inductance, but also a certain small capacitance. The Radio Amateur's Hand Book B, battery; I, induction coil; K, key; S, spark-gap; L, inductance coil; C, condenser; A, aerial. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z A simple test will enable the results of a series inductance in a line to be appreciated. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. That’s the same sort of thing that happens in the case of the inductance and condenser in the oscillating audion circuit except for one important fact. Letters of a Radio-Engineer to His Son But if they are parallel and wound the same way like the coils of Fig. 46b they will act like a single coil of greater inductance. Letters of a Radio-Engineer to His Son Close Coupled Circuits.—Open and closed circuits connected directly together with a single inductance coil. The Radio Amateur's Hand Book If we reduce the capacity, we thereby greatly reduce the storage of energy, and it is not practicable to reduce the inductance below a certain amount. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z In the case of open wires spaced 12 inches apart, the limit of commercial transmission is greater, not only because the wires are larger, but because the capacity is lower and the inductance higher. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. That’s one way of starting oscillations which damp out–to start with a charged condenser and connect an inductance across it. Letters of a Radio-Engineer to His Son If the coils are parallel but wound in opposite directions as in Fig. 46c they will have less inductance because of their mutual inductance. Letters of a Radio-Engineer to His Son For sending sets they are formed of one and two coils, a single sending coil is generally called a tuning inductance coil, while a two-coil tuner is called an oscillation transformer. The Radio Amateur's Hand Book If there is no inductance in the circuit, the interrupter stage never sets in at all, but the first stage passes directly into the third stage. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z Such a treatment increases the inductance and improves transmission. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. It is equally hard if L-C has smaller capacity and inductance than ab so that it naturally oscillates faster. Letters of a Radio-Engineer to His Son As we pull the coil out the mutual effect becomes less and finally when it is well outside the mutual inductance is very small. Letters of a Radio-Engineer to His Son Some tuning inductance coils have more than one layer, they are then called lattice wound, cellular, basket wound, honeycomb, duo-lateral, stagger wound, spider-web and slab coils. The Radio Amateur's Hand Book The cell will not, however, act as a break at all unless some inductance exists in the circuit. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z As the capacity whose effects are to be neutralized Page 58 is distributed uniformly throughout the line, the counteracting inductance must also be distributed throughout the line. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. To these condensers we connect inductances and these inductances we couple to our transmitter and receiver as shown in Fig. Letters of a Radio-Engineer to His Son That sets up oscillations in the circuit with the inductance and the capacity formed by the antenna. Letters of a Radio-Engineer to His Son COUPLING, CAPACITIVE.—Oscillation circuits when connected together by condensers instead of inductance coils. The Radio Amateur's Hand Book These bobbins can have let down into them an E-shaped piece of laminated iron, so as to complete the magnetic circuit, and thus raise the inductance of the bobbin. Hertzian Wave Wireless Telegraphy 2012-01-09T03:00:20.570Z The inductances of the figure are the actual loading coils. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. That is why I have shown a variable inductance in the circuit of the transmitting antenna. Letters of a Radio-Engineer to His Son To receive at longer wave-lengths you will need to increase the inductance of your antenna so that it will be tuned to a lower frequency. Letters of a Radio-Engineer to His Son REACTANCE.—When a circuit has inductance and the current changes in value, it is opposed by the voltage induced by the variation of the current. The Radio Amateur's Hand Book And as to inductances, we say that an inductance impedes an alternating current 138more and more the higher is the frequency. Letters of a Radio-Engineer to His Son All the foregoing leads to the generalization that the higher the frequency, the greater the opposition of an inductance to an alternating current. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The fact that iron decreases the inductance and so seriously impedes alternating currents leads us to use iron-core coils where we want high inductance. Letters of a Radio-Engineer to His Son In Table I there is given, for each of several values of the inductance of the primary coil, the shortest and the longest wave-lengths which you can expect to receive. Letters of a Radio-Engineer to His Son 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 Usually we shorten this term and speak of “inductance.” Letters of a Radio-Engineer to His Son In circuits having both resistance and capacity or resistance and inductance, both properties affect the passage of current. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Therefore we say that a coil has one henry of inductance when an electron stream 85which is increasing one ampere’s worth each second stirs up in the coil a conscientious objection of one volt. Letters of a Radio-Engineer to His Son It also depends upon how much inductance there is in the coil which you have in the antenna circuit. Letters of a Radio-Engineer to His Son REACTANCE, INDUCTIVE.—The inductive reactance is the opposition offered to the current by an inductance coil. The Radio Amateur's Hand Book There is one more effect of inductance which we must know before we can get very far with our radio. Letters of a Radio-Engineer to His Son Such a line possesses Page 52 negligible resistance, inductance, and shunt capacity. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Now all we have to do to get the right idea of inductance 104is to think of each boy as standing for the electrons in one turn of the coil. Letters of a Radio-Engineer to His Son The table gives values of inductance in the first column, and of minimum wave-length in the second. Letters of a Radio-Engineer to His Son The capacity of a condenser, inductance coil or other device capable of retaining a charge of electricity. The Radio Amateur's Hand Book If there are five turns there will be twenty-five times as much inductance, as for a single turn; and so on. Letters of a Radio-Engineer to His Son All conductors possess inductance, but straight wires used in lines have negligible inductance in most actual cases. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. I’ll tell you two things more about inductance because they will come in handy. Letters of a Radio-Engineer to His Son Anything more in the way of inductance, which the antenna circuit requires to give a desired wave-length, you may consider as loading. Letters of a Radio-Engineer to His Son COUPLING.—When two oscillation circuits are connected together either by the magnetic field of an inductance coil, or by the electrostatic field of a condenser. The Radio Amateur's Hand Book I have told you all except one of the ways in which we can affect the inductance of a circuit. Letters of a Radio-Engineer to His Son All wires which are wound into coils, such as electromagnets, possess inductance in a greatly increased degree. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. While we are at it we might just as well clean up this whole business of variable capacities and inductances by considering two ways in which to make a variable inductance. Letters of a Radio-Engineer to His Son In Table II are some data as to winding coils on straight 227cores to obtain various values of inductance. Letters of a Radio-Engineer to His Son DE TUNING.—A method of signaling by sustained oscillations in which the key when pressed down cuts out either some of the inductance or some of the capacity and hence greatly changes the wave length. The Radio Amateur's Hand Book The more turns there are included in the part of the coil which we are using the greater is the inductance. Letters of a Radio-Engineer to His Son Such a line possesses negligible resistance, inductance, and shunt capacity. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. If the coils are neither parallel nor at right angles there will be some mutual inductance but not as much as if they were parallel. Letters of a Radio-Engineer to His Son I have assumed that you will have this number of turns per inch on your coils and calculated the inductance which you should get for various numbers of total turns. Letters of a Radio-Engineer to His Son VARIOCOUPLER.—A tuning device for varying the inductance of the receiving oscillation circuits. The Radio Amateur's Hand Book That’s what we arrange to do in a variable inductance of the variometer type. Letters of a Radio-Engineer to His Son Both observations in this test show that the amount of current entering and emerging from the line decreased as the inductance increased. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. There is another way of varying the mutual inductance. Letters of a Radio-Engineer to His Son Later in this letter I shall tell you how to increase or decrease the inductance of a coil. Letters of a Radio-Engineer to His Son For the loading coils use honeycomb coils, or other good compact inductance coils, as shown in Chapter X and having a range of whatever wave length you wish to receive. The Radio Amateur's Hand Book Now we have several methods of varying capacity and inductance and therefore we are ready to vary the frequency of our audion oscillator; that is, “tune” it, as we say. Letters of a Radio-Engineer to His Son The degree in which any current is opposed by inductance is termed the reactance of that inductance. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. Suppose first that in each circuit the inductance and capacity have such values as to produce oscillations of the same frequency. Letters of a Radio-Engineer to His Son But what would happen if we should decrease the capacity and increase the inductance? Letters of a Radio-Engineer to His Son The units of inductance commonly used in radio work are the millihenry, which is the thousandth part of a henry; and the centimeter of inductance, which is one one-thousandth part of a microhenry. The Radio Amateur's Hand Book In that case we use a variable inductance as in Fig. Letters of a Radio-Engineer to His Son To distinguish the two kinds of reactance, that due to the capacity is called capacity reactance and that due to inductance is called inductive reactance. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. The inductance of a coil is very much higher if it has an iron core. Letters of a Radio-Engineer to His Son That would depend upon how much we decreased the capacity and how much we increased the inductance. Letters of a Radio-Engineer to His Son 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 We know that fact because we know that an iron core increases the inductance and so chokes the current. Letters of a Radio-Engineer to His Son There are two ways in which inductance might be introduced into a telephone line. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. In Table III is given the values of the inductance which is controlled by the switches of that figure, the corresponding number of turns, and the wave-length to which the antenna should then be tuned. Letters of a Radio-Engineer to His Son It would be possible to decrease the capacity and then if we increased the inductance just the right amount to have no change in the frequency. Letters of a Radio-Engineer to His Son To be really efficient a variometer must have a small resistance and a large inductance as well as a small dielectric loss. The Radio Amateur's Hand Book And this extra trouble would be because of the relations between gangs, that is, because of their “mutual inductance.” Letters of a Radio-Engineer to His Son The inserted inductance remaining constant, its benefits may become detriments when the other two "constants" change. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. It was the condenser and inductance which you studied in connection with Fig. Letters of a Radio-Engineer to His Son No matter how large or how small we make the capacity we can 102always make the inductance such that there isn’t any change in frequency. Letters of a Radio-Engineer to His Son By winding inductance coils with two or more layers the highest inductance values can be obtained with the least resistance. The Radio Amateur's Hand Book Try it again, but this time, as in Fig. 47d, connect the charged condenser to a coil which has inductance. Letters of a Radio-Engineer to His Son Practical results have been secured in increasing the distributed inductance by wrapping fine iron wire over each conductor of the line. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. That’s all there is to tuning–adjusting the capacity and inductance of a circuit until it has the same natural frequency as some other circuit with which we want it to work. Letters of a Radio-Engineer to His Son I’ll give you a rule for this, after I have told you some more things about capacities and inductances. Letters of a Radio-Engineer to His Son A wiring diagram of a multipoint inductance coil is shown in Fig. The Radio Amateur's Hand Book We can either adjust the capacity as we just did, or we can adjust the inductance. Letters of a Radio-Engineer to His Son He inserts inductances in series with the wires of the line, so adapting them to the constants of the circuit that attenuation and distortion are diminished in a gratifying degree. Cyclopedia of Telephony & Telegraphy Vol. 1 A General Reference Work on Telephony, etc. etc. When we do we get these mil-henries of inductance from a coil which we call a “loading coil.” Letters of a Radio-Engineer to His Son A short straight wire has a very small inductance, indeed. Letters of a Radio-Engineer to His Son The simplest kind is a transmitting inductance which consists of 25 or 30 turns of copper wire wound on an insulating tube or frame. The Radio Amateur's Hand Book The coil, LA, however, because of its inductance, tends to keep the same amount of current flowing through itself. Letters of a Radio-Engineer to His Son This coil has a small inductance but it is enough to offer a large impedance to radio-frequency currents. Letters of a Radio-Engineer to His Son It won’t make any difference if we use equal inductance coils, instead of the R-resistances, and connect the transmitter to them inductively as shown in Fig. Letters of a Radio-Engineer to His Son The longer the wire the larger will be the inductance but unless the length is hundreds of feet there isn’t much inductance anyway. Letters of a Radio-Engineer to His Son Where high frequency currents surge in a circuit the inductance of it becomes a powerful factor. The Radio Amateur's Hand Book The great advantage of using an oscillation transformer instead of a simple inductance coil is that the capacitance of the closed circuit can be very much larger than that of the aerial wire system. The Radio Amateur's Hand Book The inductance coils of the aerial wire system and those of the secondary coil circuit are practically alike. The Radio Amateur's Hand Book Likewise, by varying the capacitance and the inductance of the receptor the circuits can be tuned to receive incoming electric waves of whatever length within the limitation of the apparatus. The Radio Amateur's Hand Book You see that we can change the inductance of a coil very easily by changing the number of turns. Letters of a Radio-Engineer to His Son The primary coil is wound on a fixed cylinder and its inductance is varied by means of a sliding contact like the double slide tuning coil described above. The Radio Amateur's Hand Book Likewise an oscillation circuit has a natural frequency which depends upon its inductance, capacitance and resistance. The Radio Amateur's Hand Book Coarse Tuning.—The first adjustment in the tuning oscillation circuits of a receptor is made with the inductance coil and this tunes them coarse, or roughly. The Radio Amateur's Hand Book Fine Tuning.—After the oscillation circuits have been roughly tuned with the inductance coil the exact adjustment is obtained with the variable condenser and this is fine tuning. The Radio Amateur's Hand Book The first is that the inductance will be larger if the turns are large circles. Letters of a Radio-Engineer to His Son Now the inductance and resistance of a circuit such as is shown at A in Fig. The Radio Amateur's Hand Book VARIOMETER.—A tuning device for varying the inductance of the receiving oscillation currents. The Radio Amateur's Hand Book But if you vary the inductance of the one loop so that it is larger or smaller than that of the other loop no spark will take place in the second circuit. The Radio Amateur's Hand Book Tuning coils, sometimes called transmitting inductances and oscillation transformers, are of various types. The Radio Amateur's Hand Book The electrons don’t get started as fast because of the inductance. Letters of a Radio-Engineer to His Son In simple electric resonance an oscillating current of a given frequency flowing in a circuit having the proper inductance and capacitance may increase the voltage until it is several times greater than its normal value. The Radio Amateur's Hand Book Because of the inductance, when a current flows through a circuit it causes the electric energy to be absorbed and changes a large part of it into magnetic lines of force. The Radio Amateur's Hand Book The Oscillation Transformer.—With an oscillation transformer you can tune much more sharply than with a single inductance coil tuner. The Radio Amateur's Hand Book |
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