Electromagnets

Electromagnets

Introduction

Electric current creates the magnetic field in an electromagnet, a special kind of magnet. Wire looped around a coil is the most common building block of an electromagnet. Electromagnetism occurs when current flows through the wire, creating a magnetic field in the coil’s centre. When the current is switched off, the magnetic field dissipates. In order to increase the magnetic strength of a magnet, the turns of the wire are commonly wrapped around a magnetic core made of a ferromagnetic material such as iron. An electric current in the winding allows for rapid changes in the magnetic field of an electromagnet compared to a permanent magnet. In contrast to a permanent magnet, which does not require any power, an electromagnet relies on a steady stream of electricity to keep its magnetic field in place. Electric motors and generators, electromechanical solenoids and relays (such as those found in hard drives and MRI machines), scientific instruments and magnetic separation equipment all make use of electromagnets. Heavy iron objects, such as scrap iron and steel, can be picked up and moved with the help of electromagnets.

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Properties of electromagnets-

The following are some of the magnet’s characteristics:

• The magnetic properties of ferromagnetic materials like iron, nickel, and cobalt make them particularly attractive.
• When two opposite poles come into contact, they attract each other.
• A free-floating magnet’s directive property is that it always points north-south.

Working principle of electromagnets-

So, how exactly do they work? Let’s take a closer look at the iron nail. When it is not influenced by an electric field, why does it not generate a magnetic field?

Nails are typically made up of thousands of separate magnetic fields, which cancel each other out when atoms in the nail are oriented in random ways. These atoms are reoriented to point in the same direction under the influence of electric current. A powerful magnetic field is created when the combined fields of all these tiny magnets are added together. Reorientation occurs as the current flow rises, resulting in increased magnetic field strength. Increasing the current flow has no effect on the magnetic field generated until all particles have been completely reoriented in the same direction. The magnet is said to be saturated at this stage.

Uses of electromagnets-

Some electromagnet uses are given in the points mentioned below:

• Amplifiers
• MRI machines
• Particle Accelerators
• Magnetic Separation
• Spacecraft Propulsion Systems
• Electric Motors and Generators
• Control Switches in Relays
• Transportation
• Induction Heating
• Hard Drives

Disadvantages of electromagnet-

Electromagnetism has a few drawbacks, such as the following:

• They get really hot very quickly.
• It takes a lot of power to run.
• They have a magnetic field that can store a lot of energy. The power goes out if the electricity is cut off.

Electromagnetic fields-

Classical electromagnetic fields (EMFs) are non-quantum fields that are generated by accelerated electrical charges. A tensor in classical electrodynamics, EMFs are the classical analogue to the tensor in quantum electrodynamics. As light travels at the speed of the electromagnetic field, currents and charges interact with this field. 

One of the four fundamental forces of nature is its quantum counterpart (the others are strong interaction, weak interaction and gravitation). As an electric and a magnetic field are combined, the field can be thought of as one. A moving current (a current) generates a magnetic field, while a stationary charge (a charge) generates an electric field. 

The Lorentz force law and Maxwell’s equations describe how currents and charges interact with the electromagnetic field. The electric field exerts a significantly greater force than the magnetic field does. Electromagnetism has traditionally been thought of as a continuous, wavelike field that propagates in a wavelike fashion. 

When looking at it from the perspective of quantum field theory, this field is quantised. It can, therefore, be expressed as the Fourier sum of creation and annihilation operators in energy-momentum space, while the effects of an interacting quantum field can be studied using perturbation theory and a wide range of mathematics, including the Dyson series, correlation, Wick’s theorem, and a variety of other techniques. However, the quantum field’s generation operators create many discrete states of energy (photons) that are distinct from each other.

Magnetic core of electromagnets-

Magnetic domains are microscopic magnets in the core material of a magnetic core (typically made of iron or steel). Until the current in the electromagnet is turned on, there is no large-scale magnetic field in the iron core since the domains in the iron core point in random directions. When a current is passed through the wire, which is wrapped around the iron core, the magnetic field penetrates the iron, causing the domains to turn and align parallelly to the magnetic field. 

Their tiny magnetic fields add to the wire’s field and create a larger magnetic field that extends into the space around the magnet. Magnetism travels more easily through metal cores because of its ability to concentrate and amplify fields. The greater the magnetic field is, the more current is passed via the wire coil. Finally, all domains are aligned, and subsequent increases in current only generate modest increases in the magnetic field: this process is known as saturation. Coil cores made of magnetically soft materials tend to lose alignment when the current in the coil is switched off, resulting in a loss of the magnetic field. Although the domains are unable to change their magnetisation orientation, the core remains a weak permanent magnet.

There are two terms for this phenomenon: hysteresis and remnant magnetism. Degaussing is an option for removing the core’s remaining magnetism. As the magnetisation of the core is constantly reversed in alternating current electromagnets, the remanence contributes to motor losses.

Electromagnets all around us-

Electricity flowing through the core of the magnet may be increased or decreased to alter its strength. This is a major benefit over permanent magnets, which cannot be turned on or off. Using magnetic recording devices, modern technology mainly relies on electromagnets. As an example, tiny magnetised particles of metal are inserted onto a disc in a pattern appropriate to the saved information while saving data to an old-school computer hard drive.

 There was a time when this data was encoded in binary computer language (0s and 1s). In order to use this information, you must first convert it back to its original binary form. What is it about this device that makes it an electromagnet? A computer’s circuitry is magnetised by the current that flows through it. In tape recorders, VCRs, and other tape-based media, this is the same premise (and yes, some of you still own tape decks and VCRs). It’s because of this that magnets can sometimes cause problems with these gadgets’ memories. In order to charge your phone or tablet wirelessly, you may be utilising electromagnetic energy every day. A magnetic field is created when the charging pad is placed on a metal surface. 

Antennas on your phone and charger allow a current to pass back and forth. Electric cars, for example, can be charged by larger coils than those seen in small devices like this. It was also thanks to electromagnets that we were able to begin harnessing electricity in the first place. A magnetic field is created by the electricity coming from your wall socket in electrical gadgets, which drives the motor. The magnet’s charge is what powers the motor, not the electricity itself. As a result of the magnetic pull, they travel in a circular fashion, much like tyres do when they round an axle.

Conclusion 

The interactions of magnets and electromagnets can be compared to each other. Building blocks include the similarity of a bar magnet’s field to the field around a coil of wire with an electric current. Electricity and energy issues cover all the nitty-gritty aspects of electromagnetic devices; thus, a functional approach is probably all that is needed here. Last but not least, it is assumed that the magnetic core is not saturated with magnetic energy. The air gap’s flux density cannot be raised, no matter how much current is put through the coil, if this design were to work. Subsequent sections on specific gadgets provide more information on these ideas.