from The Century Dictionary.
- noun A magnet which owes its magnetic properties to the inductive action of an electric current.
- noun If an insulated wire is wound about a bar of soft iron and a current of electricity is passed through it, the bar becomes a temporary magnet with a north and a south pole; the end at which the current circulates through the wire in the direction of the hands of a clock, as the observer looks at it, is the south pole. In practice, an electromagnet has ordinarily a horseshoe form. It consists of two cylinders, or cores, of soft iron, fastened together at one end and each wound many times with insulated wire; the wire must be so wound that if the horseshoe were straightened the direction of winding would be the same throughout. An electromagnet may be made very powerful, so as to support a ton or more. The soft iron core retains its maximum magnetization only so long as the current is passing, and loses nearly all of it the instant the current ceases. This principle is made use of in the telegraph (which see), electric clocks, electric callbells, etc. If the core is made of steel, it becomes under the action of the current a permanent magnet.
from the GNU version of the Collaborative International Dictionary of English.
- noun A mass, usually of soft iron, but sometimes of some other magnetic metal, as nickel or cobalt, rendered temporarily magnetic by being placed within a coil of wire through which a current of electricity is passing. The metal is generally in the form of a bar, either straight, or bent into the shape of a horseshoe.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun a temporary magnet made by coiling wire around an iron core; when current flows in the coil the iron becomes a magnet
Sorry, no etymologies found.
I have a circuit breaker that hums when the dryer is running (i.e. drawing a lot of amps), but that is because it has a solenoid (based on an electro-magnet, similar to how speakers work if not exactly the same thing).
By the end of the evening I hauled out a gong-sized electro-magnet in a vain attempt to pull the compass arm north.
He together with Dr Ian Pykett were heavily involved in the installation of our first 0.1 T electro-magnet and subsequent RF and gradient coil designs.
And as Ned talked on, Mahony conceived John to himself as a kind of electro-magnet, which, once it had drawn these lesser creatures after it, switched off the current and left them to their own devices.
His ship was armed with a doze heavy guided missiles and two turrets of electro-magnet - ic guns.
In previous systems in which an electro-magnet is used, the sonorous vibrations are due either to the motion of an iron diaphragm or armature placed close to the poles of the electro-magnet, or to the expansion and contraction of the magnet itself.
[Here was shown a large electro-magnet and an induction-coil vacuum discharge spinning round and round when placed in its field.]
The lifting power of an electro-magnet of given volume is proportional to the heat generated against resistance in the wire of the magnet.
Fig. 1 represents one of the telephone receivers provided with two diaphragms or sounding boards, connected to the two limbs or cores of the U-shaped electro-magnet by short tongues.
Instead of using a diaphragm, they sometimes fix a stem to one of the cores of the electro-magnet, and mount thereon a light disk of vulcanite, wood, ivory, gutta-percha, or any other substance which it is capable of vibrating.