The watt is the power spent by a current of 1 ampere in a resistance of 1 ohm.
Supposing it is desired to make an electromagnet which shall be capable of undergoing very rapid changes of strength, it must have such a form that the coercivity of the material is overcome by a self-demagnetizing force.
The form which an electromagnetmust take will greatly depend upon the purposes for which it is to be used.
Peter Barlow, in January 1825, published in the Edinburgh Philosophical Journal, a description of such an experiment made with a view of applying Sturgeon's electromagnet to telegraphy, with results which were unfavourable.
Sturgeon's electromagnet is given as well as of other pieces of apparatus for which the Society granted him a premium and a silver medal.
The phenomena presented by theelectromagnet are interpreted by the aid of the notion of the magnetic circuit.
A design or form of electromagnet which will be very suitable for some purposes will be useless for others.
An excellent form of electromagnet for the production of very powerful fields has been designed by H.
Where it is desired that an electromagnet coil shall possess high impedance, it is usual to employ a laminated instead of a solid core.
For this reason it is usual in this type to so adjust the armature that its ends will actually strike against the pole pieces of the electromagnet when thrown into vibration.
The distinction, therefore, between an impedance coil and the coil of an ordinary electromagnet is one of function, since structurally they may be the same, and the same principles of design and construction apply largely to each.
The diaphragms became thin iron disks, instead of membranes carrying iron; the electromagnet cores were made of permanently magnetized steel instead of temporarily magnetized soft iron, and the battery was omitted from the line.
The two coils of theelectromagnet are connected together in series in such a way that current in a given direction will act to produce a north pole in one of the free poles and a south pole in the other.
So does an electromagnetcomposed of windings and iron cores.
Describe an electromagnet and its function in telephony.
Sneak currents though small, may, when allowed to flow for a long time through the winding of an electromagnet for instance, develop enough heat to char or injure the insulation.
Electromagnet with Terminals] Where economy of space is necessary, a convenient method of terminating the winding of the coil consists in fastening rigid terminals to the spool head.
When the key is closed, the electromagnet draws down the armature and lever until the latter hits a stop O, making a click.
Thus an electromagnet may be made stronger by (a) increasing the number of turns of wire in its coils and by (b) sending a stronger current through it.
The invention of an effective electromagnet by Henry made possible the electric telegraph.
The electromagnetis defined as a mass of iron around which is placed a helix for conducting an electric current.
In the relay a very small current will magnetize its electromagnet enough to draw toward it the delicately hung armature thereby closing a second circuit which contains a sounder and a battery.
A horseshoe electromagnet may have a complete iron circuit for its lines of force.
The problem of determining the magnetization of iron and other metals in the strong fields formed between the poles of an electromagnet was first attacked by J.
The metals, which were prepared in the form of small rods, were magnetized between the poles of an electromagnet and tested with a magnetometer at temperatures of -186 deg.
A no voltage release may consist of an electromagnet in series with the shunt field circuit; it holds the rheostat arm in the operating position as long as current flows through the shunt field from the line.
This lever carries a soft iron armature I, which is held by the poles of the electromagnet E, when, in starting the motor, the arm has been gradually forced over as far as it will go.
If the electromagnet be now excited and have the polarity indicated, it will be found that on passing a strong current down the wire, the index F moves toward the right, showing a similar movement in the wire.
In the operation of a dynamo with load, the induced current flowing in the armature winding, converts the armature into an electromagnet setting up a field across or at right angles to the field of the machine.
We can also wrap wires around this circular iron and make an electromagnetof it.
We Need An Electromagnet We can't reverse the poles on simple bar magnets, but we can on electromagnets.
With the power off, the electromagnet lets the spring return the armature to its normal position, contact is made again, and the cycle starts all over again--just as long as you continue to push on the button.
But in that case the magnetism of the electromagnet was so large that the polarity of the small magnet was reversed!
If that same bar magnet were held in the field of the electromagnet with its north pole pointed toward the magnet and then, by the action of some outside force of sufficient power, its polarity were reversed, the bar would be repelled.
A pillar also mounted geometrically, placed vertically in front of the carriage, carries the electromagnet style or signals and tuning-fork which can be brought into contact with the glass by means of a lever.
The wire of the second screen conveys a current through another electromagnet which supports a much shorter rod.
The wire of the first forms part of the circuit of an electromagnet which, so long as it is energized, supports a vertical rod called the "chronometer.
Should we now slip over this electromagnet a paper tube upon which has been wound with regularity a great and continuous length of No.
To unlock, push the button D, which act will cause the electromagnet to raise the latch C, when the bolt may be drawn and the door opened.
A Floating Electromagnet [152] A piece of iron placed in a coil of wire carrying a current of electricity becomes an electromagnet.
To make the best electromagnet we need qualities of iron just the opposite from those of the permanent magnet.
The earth itself is a great magnet; and there is good reason for believing that it is an electromagnet of great power.
Now revolve the arm, and every time the electromagnet or keeper approaches the permanent magnet a current of one polarity will be momentarily developed in the wire of the electromagnet, which is moving.
Another way was to connect an electromagnet (having a diaphragm or reed across its poles) in the circuit at the receiving-end and mount it on some kind of a soundboard.
A differential electromagnet is wound with two insulated wires and so connected to the battery that the current divides and passes around the iron core in opposite directions.
In the dynamo there is a discharge every time the electromagnet of the armature cuts through the lines of force of the magnetic field, and in the galvanic battery every time a molecule is broken up and its little measure of energy is set free.
This consisted of an electromagnet of considerable size, mounted upon a wooden rod about ten feet long.
It will be plain to all that we might make the electromagnet stationary and revolve the permanent magnet and get the same result.
The field may revolve or the electromagnet may revolve, whichever is the most convenient to construct.
If the permanent magnet were strong enough and the electromagnet the right size as to iron, windings, etc.
The great value of the electromagnet lies in its ability to readily discharge, or go back to the neutral state, when the current is broken.
We have already stated that an electromagnet is made by winding an insulated wire around a soft iron core.
E is the electromagnet of the relay, and R A is its armature.
The mechanical device is started by the electric current when the armature of the electromagnet is attracted.
The electromagnet is also an artificial magnet; this will be treated separately.
A strip of narrow paper is slowly pulled from the reel by the machine, a mark being made upon it every time the armature of an inclosed electromagnet is attracted.
Over the poles of the horseshoe electromagnet is an armature fixed to a metal bar that can rock up and down.
Telegraph Sounders= receive the current from some distant station, and with its electromagnetproduce sounds that can be translated into messages.
The other wire from D C passes to one end of the electromagnet coil H.
The receiver is made of hard rubber, and contains a permanent bar magnet, which is wound with wire so as to make it also an electromagnet when desired.
Here we have an electromagnet with its poles, and an iron armature wound with wire, just as in the dynamo we have described, except that its form is different.
There is another reason why we cannot use permanent magnets in a dynamo, and that is because they cannot be made to give as much magnetism as an electromagnet will give.
This is usually done by installing at each station a local battery and a very delicate and sensitive electromagnet called the relay.
To increase the strength of the electromagnet still further, the so-called horseshoe shape is used (Fig.
A horseshoe electromagnet is powerful enough to support heavy weights.
The strength of any electromagnet depends upon the number of coils wound on the iron core and upon the strength of the current which is sent through the coils.
As soon as the current ceases to flow, the electromagnet loses its magnetic power and becomes merely iron and wire without magnetic attraction.
The back and forth motion of the iron plate induces current in the electromagnet c.
The armature and the carbon-tipped poles of the electromagnet form part of the local circuit; and if the relay is actuated by a weak current the armature will be attracted but feebly.
Inasmuch as a magnet has the power of attracting to itself pieces of iron or steel, the basic importance of an electromagnet in telegraphy will be at once apparent when we consider the sounder, whose clicks are familiar to every ear.
Almost midway between the hopper and the bin is placed an electromagnet whose polar extension is so arranged as to be a little to one side of a stream of material falling from the hopper.
The poles of the electromagnet in the local circuit are hollowed out and filled up with carbon disks or powdered plumbago.
This brings us to the gist of the ingenious way in which Edison substituted the action of electrochemical decomposition for that of the electromagnet to operate a relay.
It may be observed, parenthetically, for the benefit of the lay reader, that in telegraphy the device known as the relay is a receiving instrument containing an electromagnet adapted to respond to the weak line-current.
It is thus attracted toward an adjacent electromagnet when cold and is uninfluenced when hot, and as the result motion is produced.
An ordinary relay consists of an electromagnet inserted in the main line for telegraphing, which brings a local battery and sounder circuit into play, reproducing in the local circuit the signals sent over the main line.
It consisted, generally speaking, of anelectromagnet with relays connecting with a red and a blue lamp.
The poles of the electromagnet in the local or relay circuit are hollowed out and filled up with carbon disks or powdered plumbago.
A long electromagnet was placed, edgewise, a little below the hopper, and a bin with a dividing partition in the center was placed on the floor below.
Over this was placed a circular disk of paper; an electromagnet with the embossing point connected to an arm travelled over the disk, and any signals given through the magnets were embossed on the disk of paper.
To produce the best results the poles of the horseshoe electromagnet should be unlike.
At the other end of the table place E, which is the electromagnet of the relay, and H, the electromagnet of the sounder.
To find whether a current can be generated with an electromagnet and a coil of wire having an iron core.
To find whether a current can be generated with an electromagnet and a hollow coil of wire.
The lines of force which reach out from an electromagnet will generate a current in any conductor which happens to be in the field, or which is moved across the lines.
A) Join the electromagnet with the cell and key as before (Exp.
The electromagnet is supported upon its base, as directed in ยง 407.
Rotary motion with an electromagnet and a permanent magnet.
An electromagnet does not really attain its full power immediately after the current is turned on.
You grasp the electromagnet in the right hand so that the fingers point along the winding in the direction of the current flow.
Let's wind our electromagnet like this: We place the steel bar horizontally in front of us.
Indeed, this form of electromagnet is often designed very badly, the yoke being too thin, both mechanically and magnetically, for the purpose which it has to fulfill.
I have here, thanks to the Brush Electric Engineering Company, an electromagnet of the special form that is used in the Brush arc lamp when required for the purpose of working in an alternating current circuit.
Also let the coefficient of self-induction of the electromagnet and circuit be 6 quadrants.
Many electricians, unacquainted with Helmholtz's law, have been in the habit of accounting for this by saying that there is a lag in the iron of the electromagnet cores.
He observed the throw of the galvanometer when the circuit which contained the battery and the electromagnet was opened by a key which at the same moment connected the electromagnet wires to the galvanometer.
Exciting this electromagnet with a certain battery, it was found that the attraction was greatest when the shoes were pushed to about 15 millimeters, or about one-quarter of the interpolar distance, apart.
It relates to the electromagnet of a Morse receiver of the pattern habitually used on the French telegraph lines.
For example, a copper disk or copper ring placed over the pole of a straight electromagnet so excited is violently repelled.
It clearly is an ordinary electromagnet in that respect.
Take the case of an electromagnet forming some part of the receiving apparatus of a telegraph system in which it is desired to secure very rapid working.
This method has been adopted in the Carbone arc, which, by the employment of inclined carbons, and a suitableelectromagnet to keep the true arc steady at the ends of the carbons, has achieved considerable success.
The latter consists of a long rod passing through guides, and is embraced somewhere by a ring capable of being tilted or lifted by a finger attached to the armature of an electromagnet the coils of which are in series with the arc.
The glower then takes current, becoming itself brilliantly incandescent, and the electromagnet becoming energized switches the heater coil out of circuit.
Clockwork mechanism with a regulating electromagnet moves the rods simultaneously and controls the movements of the carbons so that they are displaced at the same rate as they are consumed.
Charlie fell to work at once, mounting another electromagnet beside the one he had set up, and rigging up two more X-ray bulbs beside the packing box which held the meteor.
He mounted a powerful electromagnet just below the meteorite, and set up an X-ray tube to bombard it with rays.
J is an armature of soft iron pivoted at K and worked by the electromagnet M.
All then that is necessary is to fix a piece of iron on the anchor so that its weight pulls the anchor over one way, while an electromagnet pulls the iron the other.
On the third of them is placed an iron armature, which works between the poles of an electromagnet fixed to the case, and by which the pendulum is actuated.
The electromagnet is the thing that puts the 'go' in telegraphy, the telephone, this radio business.
The electric connection between the carbon and the coil of the electromagnet is maintained by the flexible wire, S.
C, which falls by its own weight and by the weight of the electromagnet and the carbon fixed to it.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "electromagnet" in a variety of sentences. We hope that you will now be able to make sentences using this word.
