1. (noun)electro-magnet 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
Definition of 'electro-magnet'
The Standard Electrical Dictionary
1. electro-magnet A mass, in practice always of iron, around which an electriccircuit is carried, insulated from the iron. When a current is passed through the circuit the iron presents the characteristics of a magnet. (See Magnetism, Ampére's Theory of--Solenoid--Lines of Force.) In generalterms the action of a circularcurrent is to establish lines of force that run through the axis of the circuit approximately parallel thereto, and curving out of and over the circuit, return into themselves outside of the circuit. If a mass of iron is inserted in the axis or elsewhere near such current, it multiplies within itself the lines of force, q. v. (See also Magnetic Permeability--Permeance--Magnetic Induction, Coefficient of Magnetic Susceptibility--Magnetization, Coefficient of Induced.) These lines of force make it a magnet. On their direction, which again depends on the direction of the magnetizing current, depends the polarity of the iron. The strength of an electro-magnet, below saturation of the core (see Magnetic Saturation), is proportional nearly to the ampere-turns, q. v. More turns for the samecurrent or morecurrent for the same turns increase its strength.
The shapes of electro-magnets vary greatly. The cuts show several forms of electro- magnets. A more usual form is the horseshoe or doublelimb magnet, consisting generally of two straight cores, wound with wire and connected and held parallel to each other by a bar across one end, which bar is called the yoke.
In winding such a magnet the wire coils must conform, as regards direction of the current in them to the rule for polarity already cited. If both poles are north or both are south poles, then the magnet cannot be termed a horseshoe magnet, but is merely an anomalous magnet. In the field magnets of dynamos the most varied types of electro-magnets have been used. Consequent poles are often produced in them by the direction of the windings and connections.
To obtain the most powerful magnet the iron core should be as short and thick as possible in order to diminish the reluctance of the magnetic circuit. To obtain a greater range of action a long thin shape is better, although it involves waste of energy in its excitation.
Definitions of electro-magnet
