Exploring quantum gravity and entanglement using pendulums

When it comes to a marriage with quantum theory, gravity is the lone holdout among the four fundamental forces in nature. The three others—the electromagnetic force, the weak force, which is responsible for radioactive ...

Creating a non-radiating source of electromagnetism

An international team of researchers has developed a way to create non-radiating sources of electromagnetism. In their paper published in the journal Physical Review Letters, the group describes their technique and how well ...

Energy harvesting technology based on ferromagnetic resonance

Researchers from the Graduate School of Engineering, Osaka City University have succeeded in storing electricity with the voltage generated from the conversion phenomenon of ferromagnetic resonance (FMR) using an ultra-thin ...

Metamaterials research challenges fundamental limits in photonics

Cornell researchers are proposing a new way to modulate both the absorptive and the refractive qualities of metamaterials in real time, and their findings open intriguing new opportunities to control, in time and space, the ...

Exploring the limits of light-matter coupling at the nanoscale

The interplay between light and matter encompasses a stunning spectrum of phenomena, from photosynthesis to the captivating colors of rainbows and butterfly wings. Diverse as these manifestations may be, they involve very ...

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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