electromagnets

An electromagnet is a magnet in which the magnetic field is produced by an electric current. It typically consists of a core of ferromagnetic material, such as soft iron or silicon steel, around which a coil of insulated wire is wound. When current flows through the coil, the magnetic field is generated in the core, concentrating flux and allowing the magnetism to be controlled by the electrical supply.

Construction and design factors influence performance. The core is usually laminated to reduce eddy currents in alternating-current service, and shapes vary from long solenoids to horseshoe or pot configurations. The strength of the field depends on the number of coil turns, the current, and the material’s magnetic permeability. The field in an ideal long solenoid is roughly proportional to NI/L, where N is the number of turns, I is the current, and L is the length; real cores exhibit saturation and may include air gaps that reduce flux.

Operation and characteristics. Electromagnets can be switched on and off by controlling the current, offering tunable strength and rapid response. They can produce strong, compact magnetic fields suitable for lifting, clamping, switching, or actuating devices. For direct current, heating from winding resistance is a consideration; for alternating current, laminated or powdered-iron cores help minimize energy losses.

Applications. Widely used in industry for material handling (electromagnetic lifting devices), in relays and solenoids, and in various actuators and magnetic separation systems. They are also employed in scientific instruments and certain motors and generators, where controllable magnetism is advantageous.

History and note. Practical electromagnets were developed in the early 19th century, with early demonstrations by William Sturgeon and subsequent refinements by others, establishing a foundation for modern electromechanical devices.