The Library of Work and Play: Electricity and Its Everyday Uses

ings had increased so much that I was quite ready to slight other duties, if need be, to engage in them. Moreover, since my business was education it was not difficult for me

essays to teach boys, but do

dishes were to be washed by electricity, rugs and furniture were to be cleaned by electricity, and innumerable distracting and distressing things were to take place. I told the boys that really only two kinds of

-horse-power electric motor takes the place of a boy. We found a dark and dirty corner where a boy used to stand and turn a crank every time ?sthetically inclined people enjoyed an organ recital in the room above. Science, which

it. It comes nearer than any other machine to paying back all that you put into it. It is most economical when working up

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n 1873 at the Vienna Exhibition, and by many believed to have been discovered by accident at that exhibit. But why does it look like a dynamo? It has a field whose magnetism is produced by an electric current sent through coils of wire, and it has an armature whose magnetism is likewise produce

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e line circuit. We may adjust the relative amount of wire in field and line so that any portion of the current we choose will pass through the field. The amount of current it will generate depends, (1) upon the strength of the field and (2) upon the speed of the armature. Its field, although never entirely without magnetism,

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ome out of the machine when acting as a dynamo. It will then be noticed that, although the direction of the current through the field is the same, whet

. 22. This wire, or portions of it, is introduced into the armature circuit when the machine first starts. When, however, the machine has started and the armature is moving within the influence of a magnetic field, it plays the part of a dynamo at the same time that it is acting as a motor. Two confl

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ended that this motor should run at a constant speed, as is often the case, no other governor would be needed than this counter-electro-motive force, for whenever the machine begins to go faster, on account of reduced load, its counter-electro-motive force increases as the speed and holds in check the impressed electro-motive forc

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, K, rest on the top of this and air ducts lead from this compartment to the pipes of the organ. The keys of the organ operate air cocks which open and close the air ducts connected with the organ-pipes. A chain connected with e passes around the axle of the wheel l and has a weight W upon its lower end. The wheel l carries a strip of brass n, which slides over metal points p, p, p, etc. The successive points are connected by coils of wire to furnish resistance. This series of coils is called a rheostat. The wires t and u form a loop from the armature of the motor and connect t

motor is three inches in diameter. It is connected by a flat leather belt with a wheel thirty inches in diameter. When the motor therefore, makes 1,800 revolutions per minute this wheel makes 180 revolutions per minute. The axle of this wheel carries a small cog-wheel three inches in diameter and it is connected by a chain belt with a cog wheel on the shaft S (Fig. 23). Thus this shaft revolv

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a double-pole, single-throw switch (Fig. 24),

23) is carried below the lowest point p, thus cutting off the current and stopping the motor. As soon as he

essure reaches a certain point, say sixty pounds per square inch, it automatically shuts off the electric current from the motor which works the pump. But when the motorman us

rom a compartment in the machine, and the atmosphere pressing in through nozzle and hose carries dust from rugs and furniture with it into the compartment. The best vacuum cleaners will produce a pressure of seven or eight pounds per square inch, about half

some of the exhibits. In many cases it is not necessary to have a complete electric motor, but simply an electro-magnet to do the work. In booth No. 56 you will find a piano played by electricity. Its keys are moving, but no hands strike them. There is no ghost at work here. A little strip of iron has been placed upon the under side of each key and a sm

n itself. In this case the keys simply act as push buttons to close the electric circuit through electr

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cked opens apparently of its own accord. To say that the door opens by electricity is only to add mystery. What does happen is that an electric bell up in the apartment r

multitude of electrical appliances which you meet in life is the

ng with this key alone first and note down all the applications of electro-magnets