Like artificial steel magnets, electromagnets are usually of two forms, bar and horseshoe.
When at first man tried to signal with electromagnets at a distance it was found that the current would not work the electromagnet.
Behind local dials are electromagnets which, by means of an armature working a frame and ratchet wheel, move the hands forward every minute or half-minute as the current is sent from the standard clock.
The making of various kinds of electromagnets and putting currents of electricity to work is becoming one of the great industries of mankind.
Examine the motor and see that it is made of several electromagnets which keep attracting each other around and around.
The more important type of self-exciting machine is provided with electromagnets in which the field of force is "built up" from the residual magnetism of the soft iron or steel cores of the field magnets of the dynamo itself.
Electromagnets are also used for extracting fragments of iron or steel from the eye, and for many laboratory purposes.
Electromagnets specially designed to produce a very intense magnetic field are used commercially in handling scrap-iron, pig-iron, &c.
Subsequently similar machines with electromagnets were introduced by Henry Wilde (b.
This is generally the case in the electromagnets which are employed as the field magnets in dynamo machines.
It has been found that if the sheet iron employed for cores of alternating electromagnets or transformers is heated to a temperature somewhere in the neighbourhood of 200 deg.
Wilde introduced the use of electromagnets for the field magnets.
Broadly speaking, the materials which are now employed in the manufacture of the cores of electromagnets for technical purposes of various kinds may be said to fall into three classes, namely, forgings, castings and stampings.
Inventors were then incited to construct powerful electromagnets as tested by the weight they could carry from their armatures.
The tables are also explanatory of the fact that mild steel has gradually replaced iron in the manufacture of dynamo electromagnets and transformer-cores.
In some of the mild-steel castings used for dynamo electromagnets it appears that the total foreign matter, including carbon, manganese and silicon, is not more than 0.
In connexion with the technical application of electromagnets such as those used in the field magnets of dynamos (q.
Now if you sang into the piano, you would have the rhythmic impulse that set the piano strings vibrating coming directly through the air, while with the battery the impulse would come through the wire and the electromagnets instead.
Were these transmitters and receivers made from electromagnets and strips of flat steel, as you told us the other day?
In telephony electromagnets frequently serve, as already stated, to perform other functions than the producing of motion by attracting or releasing their armatures.
The matter of bringing out the terminal ends of the winding is one that has received a great deal of attention in the construction of electromagnets and coils for various purposes.
Let inductive coils such as electromagnets be inserted serially in the wires of the line one by one, while conversation goes on.
This bends around back of the electromagnets and comes into close proximity to the armature 5.
The two electromagnets are mounted side by side, as shown, by attaching their cores to a yoke piece 1 of soft iron.
The two things principally affecting the manufacture of electromagnets for telephone purposes are the number of turns in a winding and the resistance of the wound wire.
Frequently in telephony, the electromagnets are provided with more than one winding.
Lamp Signal Controlled by Relay] The qualities of electromagnets and lamps in these respects are used to advantage by the lamp signal arrangement shown in Fig.
The selector consists of two electromagnets which are bridged in series across the telephone circuit and are of very high impedance.
The effect of neighboring fields is overcome by iron shields; this prevents theelectromagnets affecting, through overloads, the strength of the permanent magnets.
It consists of two voltmeter electromagnets acting in opposition on a disc attached to the pointer shaft.
Home-Made Electric Clock [268] The clock illustrated herewith is driven by means of electromagnets acting directly on the pendulum bob.
If you are able to secure the electromagnets from a discarded electric bell they will work fine for the magnets M1 and M2.
B is an ordinary vibrating electric bell, M1 and M2 are the two electromagnets of the annunciator, A is a battery of several dry cells, and P1 and P2 are the push buttons from either of which the bell may be operated.
The electromagnets and other actuating mechanism cannot be seen plainly in this figure, but are produced diagrammatically in Fig.
It will be understood that electromagnets were the ticker's actuating agency.
In the case of electromagnets the magnetic circuit becomes closed when the armature touches both poles at the same time.
A nail or screw wound with insulated wire can be used for theelectromagnets of a home-made annunciator.
The armatures of electromagnets are usually arranged so that they can not quite touch the cores, to avoid this sticking.
Some experiments illustrating practical uses of electromagnetswill be given in a future chapter.
For electromagnets it will be necessary to support the edges of the paper with books, etc.
A) Use the two electromagnets joined to the connecting plates (Fig.
They contain electromagnets so arranged that when the armature is attracted by the pushing of a button anywhere in the building, the door can be pushed open.
Two electromagnets are shown, one being generally joined to a white push-button for turning on the gas and lighting it, the other being joined to a black button which turns off the gas when it is pressed.
They contain electromagnets which are connected to push-buttons located in the building, and which bring the numbers into place as soon as the current passes through them.
Thus you will see that there are very good reasons for using electromagnets in making dynamo-machines.
The magnets made of iron are called electromagnets because they exhibit magnetism only when the amperes of current of electricity are flowing around them.
Let us see now how these electromagnets and dynamos are made, and then examine the methods which are followed to operate and use them.
From these experimental results I pass to the special design of electromagnets for special purposes.
There must be a wider width between the poles than is desirable in electromagnets for traction.
Now I want particularly to ask you to guard against the idea that all these results obtained from electromagnets are equally applicable to permanent magnets of steel; they are not, for this simple reason.
Hence the cause of the commonly received opinion among telegraph engineers that for rapid work electromagnets must have short cores.
Vaschy,[1] respecting the coefficients of self-induction of the electromagnets of a number of pieces of telegraphic apparatus.
Many two-pole electromagnets show a tendency to bend together when the current is turned on.
We have already laid down the principle which will enable us to design electromagnets to act at a distance.
Several times it has been proposed to increase the power of electromagnets by constructing them with intermediate masses of iron between the central core and the outside, between the layers of windings.
The electromagnets in American patterns of telegraphic apparatus usually have shorter cores, and a relatively greater thickness of winding upon them, than those of European patterns.
They have a large number of poles and inductors in order to obtain the desired frequency, without excessive speed, and electromagnets instead of permanent magnets.
The usual construction is to have a stationary field-magnet and then a series of electromagnets mounted and revolving upon a shaft in the center of the magnetic field.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "electromagnets" in a variety of sentences. We hope that you will now be able to make sentences using this word.
