Fig. 30-31. Field Winding, Series-woundFigs. 30-31.Field Winding, Series-wound
Series-wound Field.—Fig.31shows a "series-wound" dynamo. The wires of the fields (A) are connected up in series with the brushes of the armature (D), and the wires (G, G') are led out and connected up with a lamp, motor or other mechanism. In this case, as well as in Figs.32and33, both the field and the armature are made of soft gray iron. With this winding and means of connecting the wires, the field is constantly excited by the current passing through the wires.
Shunt-wound Field.—Fig.32represents what is known as a "shunt-wound" dynamo. Here thep. 48field wires (H, H) connect with the opposite brushes of the armature, and the wires (I, I') are also connected with the brushes, these two wires being provided to perform the work required. This is a more useful form of winding for electroplating purposes.
Figs. 32-33. Shunt-wound, Compound-woundFigs. 32-33.Shunt-wound, Compound-wound
Compound-wound Field.—Fig.33is a diagram of a "compound-wound" dynamo. The regular field winding (J) has its opposite ends connected directly with the armature brushes. There is also a winding, of a comparatively few turns, of a thicker wire, one terminal (K) of which is connected with one of the brushes and the other terminal (K') forms one side of the lighting circuit. A wire (L) connects with the other armature brush to form a complete lighting circuit.
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Measuring Instruments.—The production of an electric current would not be of much value unless we had some way by which we might detect and measure it. The pound weight, the foot rule and the quart measure are very simple devices, but without them very little business could be done. There must be a standard of measurement in electricity as well as in dealing with iron or vegetables or fabrics.
As electricity cannot be seen by the human eye, some mechanism must be made which will reveal its movements.
The Detector.—It has been shown in the preceding chapter that a current of electricity passing through a wire will cause a current to pass through a parallel wire, if the two wires are placed close together, but not actually in contact with each other. An instrument which reveals this condition is called agalvanometer. It not only detects the presence of a current, but it shows the direction of its flow. We shall now see how this is done.
For example, the wire (A, Fig.35) is connectedp. 50up in an electric circuit with a permanent magnet (B) suspended by a fine wire (C), so that the magnet (B) may freely revolve.
Figs. 34-36. To the right, Compass Magnet, To the leftFigs. 34-36.To the right,Compass Magnet, To the left
For convenience, the magnetic field is shown flowing in the direction of the darts, in which the dart (D) represents the current within the magnet (B) flowing toward the north pole, and the darts (E) showing the exterior current flowing toward the south pole. Now, if the wire (A) is brought up close to the magnet (B), and a current passed through A, the magnet (B) will be affected. Fig.35shows the normal condition of the magnetized bar (B) parallel with the wire (A) when a current is not passing through the latter.
Direction of Current.—If the current should go through the wire (A) from right to left, as shown in Fig.34, the magnet (B) would swing in the direction taken by the hands of a clock and assume the position shownp. 51in Fig.34. If, on the other hand, the current in the wire (A) should be reversed or flow from left to right, the magnet (B) would swing counter-clock-wise, and assume the position shown in Fig.36. The little pointer (G) would, in either case, point in the direction of the flow of the current through the wire (A).
Fig. 37. Indicating Direction of CurrentFig. 37.Indicating Direction of Current
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Simple Current Detector.—A simple current detector may be made as follows:
Prepare a base 3' × 4' in size and 1 inch thick. At each corner of one end fix a binding post, as at A, A', Fig.37. Then select 20 feet of No. 28 cotton-insulated wire, and make a coil (B) 2 inches in diameter, leaving the ends free, so they may be affixed to the binding posts (A, A'). Now glue or nail six blocks (C) to the base, each block being 1" × 1" × 2", and lay the coil on these blocks. Then drive an L-shaped nail (D) down into each block, on the inside of the coil, as shown, so as to hold the latter in place.
Fig. 38. The BridgeFig. 38.The Bridge
Now make a bridge (E, Fig.38) of a strip of brass ½ inch wide, 1/16 inch thick and long enough to span the coil, and bend the ends down, as at F, so as to form legs. A screw hole (G) is formed in each foot, so it may be screwed to the base.
Midway between the ends this bridge has a transverse slot (H) in one edge, to receive therein thep. 53pivot pin of the swinging magnet. In order to hold the pivot pin in place, cut out an H-shaped piece of sheet brass (I), which, when laid on the bridge, has its ends bent around the latter, as shown at J, and the crossbar of the H-shaped piece then will prevent the pivot pin from coming out of the slot (H).
Fig. 39. Details of DetectorFig. 39.Details of Detector
The magnet is made of a bar of steel (K, Fig.39) 1½ inches long, ⅜ inch wide and 1/16 inch thick, a piece of a clock spring being very serviceable for this purpose. The pivot pin is made of an ordinary pin (L), and as it is difficult to solder the steel magnet (K) to the pin, solder only a small disc (M) to the pin (L). Then bore a hole (N) through the middle of the magnet (K), larger in diameter than the pin (L), and, after putting the pin in the hole, pour sealing wax into the hole, and thereby secure the two parts together. Near the upper end of the pin (L) solder the end of a pointer (O), this pointer being at right angles to the armature (K). It is betterp. 54to have a metal socket for the lower end of the pin. When these parts are put together, as shown in Fig.37, a removable glass top, or cover, should be provided.
This is shown in Fig.40, in which a square, wooden frame (P) is used, and a glass (Q) fitted into the frame, the glass being so arranged that when the cover is in position it will be in close proximity to the upper projecting end of the pivot pin (L), and thus prevent the magnet from becoming misplaced.
Fig. 40. Cross Section of DetectorFig. 40.Cross Section of Detector
How to Place the Detector.—If the detector is placed north and south, as shown by the two markings, N and S (Fig.37), the magnet bar will point north and south, being affected by the earth's magnetism; but when a current of electricity flows through the coil (B), the magnet will be deflected to the right or to the left, so that the pointer (O) will then show the direction in which thep. 55current is flowing through the wire (R) which you are testing.
The next step of importance is tomeasurethe current, that is, to determine its strength or intensity, as well as the flow or quantity.
Different Ways of Measuring a Current.—There are several ways to measure the properties of a current, which may be defined as follows:
1.The Sulphuric Acid Voltameter.—By means of an electrolytic action, whereby the current decomposes an acidulated solution—that is, water which has in it a small amount of sulphuric acid—and then measuring the gas generated by the current.
2.The Copper Voltameter.—By electro-chemical means, in which the current passes through plates immersed in a solution of copper sulphate.
3.The Galvanoscope.—By having a coil of insulated wire, with a magnet suspended so as to turn freely within the coil, forming what is called a galvanoscope.
4.Electro-magnetic Method.—By using a pair of magnets and sending a current through the coils, and then measuring the pull on the armature.
5.The Power or Speed Method.—By using an electric fan, and noting the revolutions produced by the current
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6.The Calorimeter.—By using a coil of bare wire, immersed in paraffine oil, and then measuring the temperature by means of a thermometer.
Fig. 41. Acid VoltameterFig. 42. Copper VoltameterFig. 41.Acid VoltameterFig. 42.Copper Voltameter
7.The Light Method.—Lastly, by means of an electric light, which shows, by its brightness, a greater or less current.
The Preferred Methods.—It has been found that the first and second methods are the onlyp. 57ones which will accurately register current strength, and these methods have this advantage—that the chemical effect produced is not dependent upon the size or shape of the apparatus or the plates used.
How to Make a Sulphuric Acid Voltameter.—In Fig.41is shown a simple form of sulphuric acid voltameter, to illustrate the first method. A is a jar, tightly closed by a cover (B). Within is a pair of platinum plates (C, C), each having a wire (D) through the cover. The cover has a vertical glass tube (E) through it, which extends down to the bottom of the jar, the electrolyte therein being a weak solution of sulphuric acid. When a current passes through the wires (D), the solution is partially decomposed—that is, converted into gas, which passes up into the vacant space (F) above the liquid, and, as it cannot escape, it presses the liquid downwardly, and causes the latter to flow upwardly into the tube (E). It is then an easy matter, after the current is on for a certain time, to determine its strength by the height of the liquid in the tube.
How to Make a Copper Voltameter.—The second, or copper voltameter, is shown in Fig.42. The glass jar (A) contains a solution of copper sulphate, known in commerce as blue vitriol. Ap. 58pair of copper plates (B, B') are placed in this solution, each being provided with a connecting wire (C). When a current passes through the wires (C), one copper plate (B) is eaten away and deposited on the other plate (B'). It is then an easy matter to take out the plates and find out how much in weight B' has gained, or how much B has lost.
In this way, in comparing the strength of, say, two separate currents, one should have each current pass through the voltameter the same length of time as the other, so as to obtain comparative results.
It is not necessary, in the first and second methods, to consider the shapes, the sizes of the plates or the distances between them. In the first method the gas produced, within a given time, will be the same, and in the second method the amount deposited or eaten away will be the same under all conditions.
Disadvantages of the Galvanoscope.—With the third method (using the galvanoscope) it is necessary, in order to get a positively correct reading instrument, to follow an absolutely accurate plan in constructing each part, in every detail, and great care must be exercised, particularly in winding. It is necessary also to be very careful inp. 59selecting the sizes of wire used and in the number of turns made in the coils.
This is equally true of the fourth method, using the electro-magnet, because the magnetic pull is dependent upon the size of wire from which the coils are made and the number of turns of wire.
Objections to the Calorimeter.—The calorimeter, or sixth method, has the same objection. The galvanoscope and electro-magnet do not respond equally to all currents, and this is also true, even to a greater extent, with the calorimeter.
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Understanding Terms.—We must now try to ascertain the meaning of some of the terms so frequently used in connection with electricity. If you intended to sell or measure produce or goods of any kind, it would be essential to know how many pints or quarts are contained in a gallon, or in a bushel, or how many inches there are in a yard, and you also ought to know just what the quantity termbushelor the measurementyardmeans.
Intensity and Quantity.—Electricity, while it has no weight, is capable of being measured by means of its intensity, or by its quantity. Light may be measured or tested by its brilliancy. If one light is of less intensity than another and both of them receive their impulses from the same source, there must be something which interferes with that light which shows the least brilliancy. Electricity can also be interfered with, and this interference is calledresistance.
Voltage.—Water may be made to flow with greater or less force, or velocity, through a pipe, the degree of same depending upon the height ofp. 61the water which supplies the pipe. So with electricity. It may pass over a wire with greater or less force under one condition than another. This force is called voltage. If we have a large pipe, a much greater quantity of water will flow through it than will pass through a small pipe, providing the pressure in each case is alike. This quantity in electricity is calledamperage.
In the case of water, a column 1" × 1", 28 inches in height, weighs 1 pound; so that if a pipe 1 inch square draws water from the bottom it flows with a pressure of 1 pound. If the pipe has a measurement of 2 square inches, double the quantity of water will flow therefrom, at the same pressure.
Amperage.—If, on the other hand, we have a pipe 1 inch square, and there is a depth of 56 inches of water in the reservoir, we shall get as much water from the reservoir as though we had a pipe of 2 square inches drawing water from a reservoir which is 28 inches deep.
Meaning of Watts.—It is obvious, therefore, that if we multiply the height of the water in inches with the area of the pipe, we shall obtain a factor which will show how much water is flowing.
Here are two examples:
Thus the two problems are equal.
A Kilowatt.—Now, in electricity, remembering that the height of the water corresponds withvoltagein electricity, and the size of the pipe withamperage, if we multiply volts by amperes, or amperes by volts, we get a result which is indicated by the termwatts. One thousand of these watts make a kilowatt, and the latter is the standard of measurement by which a dynamo or motor is judged or rated.
Thus, if we have 5 amperes and 110 volts, the result of multiplying them would be 550 watts, or 5 volts and 110 amperes would produce 550 watts.
A Standard of Measurement.—But with all this we must have some standard. A bushel measure is of a certain size, and a foot has a definite length, so in electricity there is a recognized force and quantity which are determined as follows:
The Ampere Standard.—It is necessary, first, to determine what an ampere is. For this purpose a standard solution of nitrate of silver isp. 63used, and a current of electricity is passed through this solution. In doing so the current deposits silver at the rate of 0.001118 grains per second for each ampere.
The Voltage Standard.—In order to determine the voltage we must know something ofresistance. Different metals do not transmit a current with equal ease. The size of a conductor, also, is an important factor in the passage of a current. A large conductor will transmit a current much better than a small conductor. We must therefore have a standard for theohm, which is the measure of resistance.
The Ohm.—It is calculated in this way: There are several standards, but the one most generally employed is theInternational Ohm. To determine it, by this system, a column of pure mercury, 106.3 millimeters long and weighing 14.4521 grams, is used. This would make a square tube about 94 inches long, and a little over 1/25 of an inch in diameter. The resistance to a current flow in such a column would be equal to 1 ohm.
Calculating the Voltage.—In order to arrive at the voltage we must use a conductor, which, with a resistance of 1 ohm, will produce 1 ampere. It must be remembered that the volt is the practical unit of electro-motive force
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While it would be difficult for the boy to conduct these experiments in the absence of suitable apparatus, still, it is well to understand thoroughly how and why these standards are made and used.
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Simple Switches.—We have now gone over the simpler or elementary outlines of electrical phenomena, and we may commence to do some of the practical work in the art. We need certain apparatus to make connections, which will be constructed first.
A Two-Pole Switch.—A simple two-pole switch for a single line is made as follows:
A base block (A, Fig.43) 3 inches long, 2 inches wide and ¾ inch thick, has on it, at one end, a binding screw (B), which holds a pair of fingers (C) of brass or copper, these fingers being bent upwardly and so arranged as to serve as fingers to hold a switch bar (D) between them. This bar is also of copper or brass and is pivoted to the fingers. Near the other end of the base is a similar binding screw (E) and fingers (F) to receive the blade of the switch bar. The bar has a handle (G) of wood. The wires are attached to the respective binding screws (B, E).
Double-Pole Switch.—A double-pole switch or a switch for a double line is shown in Fig.44.p. 66This is made similar in all respects to the one shown in Fig.43, excepting that there are two switch blades (A, A) connected by a cross bar (B) of insulating material, and this bar carries the handle (C).
Fig. 43. Two-Pole SwitchFig. 43.Two-Pole Switch
Fig. 44. Double-Pole SwitchFig. 44.Double-Pole Switch
Other types of switch will be found very useful. In Fig.45is a simple sliding switch in which the base block has, at one end, a pair of copper plates (A, B), each held at one end to the base by a binding screw (C), and having a bearing or contact surface (D) at its other end. At thep. 67other end of the base is a copper plate (E) held by a binding screw (F), to the inner end of which plate is hinged a swinging switch blade (G), the free end of which is adapted to engage with the plates (A, B).
Fig. 45. Sliding SwitchFig. 45.Sliding Switch
Sliding Switch.—This sliding switch form may have the contact plates (A, B and C, Fig.46) circularly arranged and any number may be located on the base, so they may be engaged by a single switching lever (H). It is the form usually adopted for rheostats.
Reversing Switch.—A reversing switch is shown in Fig.47. The base has two plates (A, B) at one end, to which the parallel switch bars (C, D) are hinged. The other end of the base has three contact plates (E, F, G) to engage thep. 68swinging switch bars, these latter being at such distance apart that they will engage with the middle and one of the outer plates. The inlet wires, positive and negative, are attached to the plates (A, B, respectively), and one of the outlet wires (H) is attached to the middle contact plate (F), while the other wire is connected up with both of the outside plates. When the switch bars (C, D) are thrown to the left so as to be in contact with E, F, the outside plate (E) and the middle plate (F) will be positive and negative, respectively; but when the switch is thrown to the right, as shown in the figure, plate F becomes positive and plate E negative, as shown.
Fig. 46. Rheostat Form of SwitchFig. 46.Rheostat Form of Switch
Push Buttons.—A push button is but a modified structure of a switch, and they are serviceablep. 69because they are operating, or the circuit is formed only while the finger is on the button.
Fig. 47. Reversing SwitchFig. 47.Reversing Switch
In its simplest form (Fig.48) the push button has merely a circular base (A) of insulating material, and near one margin, on the flat side, is a rectangular plate (B), intended to serve as a contact plate as well as a means for attaching one of the wires thereto. In line with this plate is a spring finger (C), bent upwardly so that it is normally out of contact with the plate (B), its end being held by a binding screw (D). To effect contact, the spring end of the finger (C) is pressed against the bar (B), as at E. This is enclosed in a suitable casing, such as will readily suggest itself to the novice.
Electric Bell.—One of the first things the boyp. 70wants to make, and one which is also an interesting piece of work, is an electric bell.
To make this he will be brought, experimentally, in touch with several important features in electrical work. He must make a battery for the production of current, a pair of electro-magnets to be acted upon by the current, a switch to control it, and, finally, he must learn how to connect it up so that it may be operated not only from one, but from two or more push buttons.
Fig. 48. Push ButtonFig. 48.Push Button
How Made.—In Fig.49is shown an electric bell, as usually constructed, so modified as to show the structure at a glance, with its connections. A is the base, B, B' the binding posts for the wires, C, C the electro-magnets, C' the bracket for holding the magnets, D the armature, E the thin spring which connects the armature with the post F, G the clapper arm, H the bell, I the adjusting screw on the post J, K the wire lead from thep. 71binding post B to the first magnet, L the wire which connects the two magnets, M the wire which runs from the second magnet to the post J, and N a wire leading from the armature post to the binding post B'.
Fig. 49. Electric BellFig. 49.Electric Bell
The principle of the electric bell is this: In looking at Fig.49, you will note that the armature bar D is held against the end of the adjustingp. 72screw by the small spring E. When a current is turned on, it passes through the connections and conduits as follows: Wire K to the magnets, wire M to the binding post J, and set screw I, then through the armature to the post F, and from post F to the binding post B'.
Fig. 50. Armature of Electric BellFig. 50.Armature of Electric Bell
Electric Bell—How Operated.—The moment a current passes through the magnets (C, C), the core is magnetized, and the result is that the armature (D) is attracted to the magnets, as shown by the dotted lines (O), when the clapper strikes the bell. But when the armature moves over to the magnet, the connection is broken between the screw (I) and armature (D), so that the cores of the magnets are demagnetized and lose their pull, and the spring (E) succeeds in drawingp. 73back the armature. This operation of vibrating the armature is repeated with great rapidity, alternately breaking and re-establishing the circuit, by the action of the current.
In making the bell, you must observe one thing, the binding posts (B, B') must be insulated from each other, and the post J, or the post F, should also be insulated from the base. For convenience we show the post F insulated, so as to necessitate the use of wire (N) from post (F) to binding post (B').
The foregoing assumes that you have used a cast metal base, as most bells are now made; but if you use a wooden base, the binding posts (B, B') and the posts (F, J) are insulated from each other, and the construction is much simplified.
It is better, in practice, to have a small spring (P, Fig.50) between the armature (D) and the end of the adjusting screw (I), so as to give a return impetus to the clapper. The object of the adjusting screw is to push and hold the armature close up to the ends of the magnets, if it seems necessary.
If two bells are placed on the base with the clapper mounted between them, both bells will be struck by the swinging motion of the armature.
An easily removable cap or cover is usuallyp. 74placed over the coils and armature, to keep out dust.
A very simple annunciator may be attached to the bell, as shown in the following figures:
Figs. 51-54. AnnunciatorFigs. 51-54.Annunciator
Annunciators.—Make a box of wood, with a base (A) 4" × 5" and ½ inch thick. On this you can permanently mount the two side pieces (B) and two top and bottom pieces (C), respectively,p. 75so they project outwardly 4½ inches from the base. On the open front place a wood or metal plate (D), provided with a square opening (D), as in Fig.54, near its lower end. This plate is held to the box by screws (E).
Within is a magnet (F), screwed into the base (A), as shown in Fig.51; and pivoted to the bottom of the box is a vertical armature (G), which extends upwardly and contacts with the core of the magnet. The upper end of the armature has a shoulder (H), which is in such position that it serves as a rest for a V-shaped stirrup (I), which is hinged at J to the base (C). This stirrup carries the number plate (K), and when it is raised to its highest point it is held on the shoulder (H), unless the electro-magnet draws the armature out of range of the stirrup. A spring (L) bearing against the inner side of the armature keeps its upper end normally away from the magnet core. When the magnet draws the armature inwardly, the number plate drops and exposes the numeral through the opening in the front of the box. In order to return the number plate to its original position, as shown in Fig.51, a vertical trigger (M) passes up through the bottom, its upper end being within range of one of the limbs of the stirrup.
This is easily made by the ingenious boy, andp. 76will be quite an acquisition to his stock of instruments. In practice, the annunciator may be located in any convenient place and wires run to that point.
Fig. 55. Alarm Switch on WindowFig. 55.Alarm Switch on Window
Fig. 56. Burglar Alarm Attachment to WindowFig. 56.Burglar Alarm Attachment to Window
Burglar Alarm.—In order to make a burglar alarm connection with a bell, push buttons or switches may be put in circuit to connect with thep. 77windows and doors, and by means of the annunciators you may locate the door or window which has been opened. The simplest form of switch for a window is shown in the following figures:
The base piece (A), which may be of hard rubber or fiber, is ¼ inch thick and 1" × 1½" in size.
Fig. 57. Burglar Alarm ContactFig. 57.Burglar Alarm Contact
At one end is a brass plate (B), with a hole for a wood screw (C), this screw being designed to pass through the plate and also into the window-frame, so as to serve as a means of attaching one of the wires thereto. The inner end of the plate has a hole for a round-headed screw (C') that also goes through the base and into the window-frame. It also passes through the lower end of the heart-shaped metal switch-piece (D)
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The upper end of the base has a brass plate (E), also secured to the base and window by a screw (F) at its upper end. The heart-shaped switch is of such length and width at its upper end that when it is swung to the right with one of the lobes projecting past the edge of the window-frame, the other lobe will be out of contact with the plate (E).
Fig. 58. Neutral Position of ContactFig. 58.Neutral Position of Contact
The window sash (G) has a removable pin (H), which, when the sash moves upwardly, is in the path of the lobe of the heart-shaped switch, as shown in Fig.56, and in this manner the pin (H) moves the upper end of the switch (D) inwardly, so that the other lobe contacts with the plate (E), and establishes an electric circuit, as shown in Fig.57. During the daytime the pin (H) may be removed, and in order to protect the switchp. 79the heart-shaped piece (D) is swung inwardly, as shown in Fig.58, so that neither of the lobes is in contact with the plate (E).
Wire Circuiting.—For the purpose of understanding fully the circuiting, diagrams will be shown of the simple electric bell with two push buttons; next in order, the circuiting with an annunciator and then the circuiting necessary for a series of windows and doors, with annunciator attachments.
Fig. 59. Circuiting for Electric BellFig. 59.Circuiting for Electric Bell
Circuiting System with a Bell and Two Push Buttons.—Fig.59shows a simple circuiting system which has two push buttons, although any number may be used, so that the bell will ring when the circuit is closed by either button.
The Push Buttons and the Annunciator Bells.—Fig.60shows three push buttons and an annunciator for each button. These three circuitsp. 80are indicated by A, B and C, so that when either button makes contact, a complete circuit is formed through the corresponding annunciator.
Fig. 60. AnnunciatorsFig. 60.Annunciators
Fig. 61. Wiring System for a HouseFig. 61.Wiring System for a House
Wiring Up a House.—The system of wiring up a house so that all doors and windows will be connected to form a burglar alarm outfit, is shown in Fig.61. It will be understood that, in practice, the bell is mounted on or at the annunciator, andp. 81that, for convenience, the annunciator box has also a receptacle for the battery. The circuiting is shown diagramatically, as it is called, so as fully to explain how the lines are run. Two windows and a door are connected up with an annunciator having three drops, or numbers 1, 2, 3. The circuit runs from one pole of the battery to the bell and then to one post of the annunciator. From the other post a wire runs to one terminal of the switch at the door or window. The other switch terminal has a wire running to the other pole of the battery.
A, B, C represent the circuit wires from the terminals of the window and door switches, to the annunciators.
It is entirely immaterial which side of the battery is connected up with the bell.
From the foregoing it will readily be understood how to connect up any ordinary apparatus, remembering that in all cases the magnet must be brought into the electric circuit.
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Storing Up Electricity.—In the foregoing chapters we have seen that, originally, electricity was confined in a bottle, called the Leyden jar, from which it was wholly discharged at a single impulse, as soon as it was connected up by external means. Later the primary battery and the dynamo were invented to generate a constant current, and after these came the second form of storing electricity, called the storage or secondary battery, and later still recognized as accumulators.
The Accumulator.—The termaccumulatoris, strictly speaking, the more nearly correct, as electricity is, in reality, "stored" in an accumulator. But when an accumulator is charged by a current of electricity, a chemical change is gradually produced in the active element of which the accumulator is made. This change or decomposition continues so long as the charging current is on. When the accumulator is disconnected from the charging battery or dynamo, and its terminals are connected up with a lighting system, or with a motor, for instance, a reverse process is setp. 83up, or the particles re-form themselves into their original compositions, which causes a current to flow in a direction opposite to that of the charging current.
It is immaterial to the purposes of this chapter, as to the charging source, whether it be by batteries or dynamos; the same principles will apply in either case.