Surface waves can help nanostructured devices keep their cool

Due to the continuing progress in miniaturization of silicon microelectronic and photonic devices, the cooling of device structures is increasingly challenging. Conventional heat transport in bulk materials is dominated by ...

On the trail of causes of radiation events during space flight

Scientists have made significant progress in understanding the sources of radiation events that could impact human space-flight operations. Relativistic electron precipitation (REP) events are instances when high energy electrons ...

The return of the spin echo

A research team from Garching and Vienna discovered a remarkable echo effect that offers exciting new possibilities for working with quantum information.

Collaboration makes crystal-clear study of radiation reaction

Place a charged particle in an electromagnetic field and the particle will accelerate and give off radiation. Typically, the emitted radiation has little effect on the particle's motion. However, if the acceleration is extremely ...

Resonant tunneling diode oscillators for terahertz-wave detection

A semiconductor device that is promising for both generating and detecting terahertz radiation has been demonstrated by physicists at RIKEN. This may aid the development of high-performance integrated solutions for terahertz ...

Physicists make electrical nanolasers even smaller

Researchers from the Moscow Institute of Physics and Technology and King's College London cleared the obstacle that had prevented the creation of electrically driven nanolasers for integrated circuits. The approach, reported ...

Scientists develop a technique to dynamically curve a photon jet

Scientists at Tomsk Polytechnic University jointly with international colleagues have found a simple technique to dynamically curve a photonic jet, turning it into a photonic hook. The method was published in Optics Letters. ...

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Electromagnet

An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off. Electromagnets are widely used as components of other electrical devices, such as motors, generators, relays, loudspeakers, hard disks, MRI machines, scientific instruments, and magnetic separation equipment, as well as being employed as industrial lifting electromagnets for picking up and moving heavy iron objects like scrap iron.

An electric current flowing in a wire creates a magnetic field around the wire (see drawing below). To concentrate the magnetic field, in an electromagnet the wire is wound into a coil with many turns of wire lying side by side. The magnetic field of all the turns of wire passes through the center of the coil, creating a strong magnetic field there. A coil forming the shape of a straight tube (a helix) is called a solenoid; a solenoid that is bent into a donut shape so that the ends meet is called a toroid. Much stronger magnetic fields can be produced if a "core" of ferromagnetic material, such as soft iron, is placed inside the coil. The ferromagnetic core increases the magnetic field to thousands of times the strength of the field of the coil alone, due to the high magnetic permeability μ of the ferromagnetic material. This is called a ferromagnetic-core or iron-core electromagnet.

The direction of the magnetic field through a coil of wire can be found from a form of the right-hand rule. If the fingers of the right hand are curled around the coil in the direction of current flow (conventional current, flow of positive charge) through the windings, the thumb points in the direction of the field inside the coil. The side of the magnet that the field lines emerge from is defined to be the north pole.

The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be rapidly manipulated over a wide range by controlling the amount of electric current. However, a continuous supply of electrical energy is required to maintain the field.

This text uses material from Wikipedia, licensed under CC BY-SA