Electromagnetism

What Are Electromagnets?

This article explains What Are Electromagnets in detail. The electromagnets are temporary magnets that are created when the electricity passes through a metal wire coil. When electricity passes through the metal coil, the electric field creates the magnetic field at the core or centre of the coil. This magnetic field can be made more powerful by introducing an iron rod in the centre of the coil. Since iron metal has the intrinsic property to retain the magnetic field the insertion of the iron rod at the centre make it a powerful magnet but it is a temporary magnet.

When the current is turned off, the iron rod with powerful magnetic core becomes a simple iron rod without magnetic property. These magnets are different from permanent magnets as permanent magnets do not require electricity to create the magnetic field. The change in the strength of the magnetic field created by the electric current passing through the coil is by changing the amount of electric current.

What Are Electromagnets

What Are Electromagnets

History of Electromagnets

Electromagnets work on the principles of electromagnetism and they create electromagnetic fields. The electromagnetic fields are the combination of two fields, namely, electric fields and magnetic fields. In 1820, a Danish scientist Hans Christian Oersted had demonstrated that whenever the current passes through the wire a nearby compass needle deflects. In 1824, the British scientist William Sturgeon invented the electromagnet by using a painted horseshoe-shaped iron piece wrapped around by bare copper wire. Sturgeon also displayed the power of this electromagnet by lifting other iron scraps. In 1830, US scientist Joseph Henry made more sophisticated electromagnet and made it popularize.

Making and uses of Electromagnets

In a simple arrangement, requires an insulated copper wire, iron rod and battery. Electromagnets are easy to make. Take some meters of insulated copper wire and wrap it around the iron or steel core. When an electric current passes through it the iron core becomes magnetized. A solenoid is the iron rod, which is wrapped up with insulated copper wire.

The strength of the magnetic field is proportional to the number of turns made around the iron core and how tightly they are wrapped around. Before the passage of current through the iron rod, atoms of the iron rod are randomly packed. When current is passed, they start to rearrange themselves in in the direction of the magnetic field generated. Once arranged in the same direction the magnetic field starts to grow.

Now while increasing the amount of current, the magnetic field grows rapidly and reaches to maximum strength. After reaching the maximum strength, an increase in the electric field does not result in increased magnetism. By stopping the current, the magnetic field becomes zero and the atoms which aligned earlier return to its natural random state.

Advantage of the electromagnets is that they are not permanent magnets and they can be made stronger by giving more amount of electricity. Also, the poles of these magnets can change by changing the direction of the current. By using this property of electromagnets, magnetic separators are made, industrially. This magnetic separator is used to separate iron scrap from a heap of scrap. Usage of electromagnets is popular where controllable magnetic flux is required in such a way that it can be varied, reversed or switched on and off.

Other devices which using electromagnets are generators, motors, loudspeakers, computer hard disks, spacecraft propulsion systems, MRIs, particle accelerators, cyclotrons, control switches etc. Modern-day technologies rely on the use of electromagnets to store data and information. Magnetic tapes, hard disks, tape recorders are some examples.

Advantages and Disadvantages of Electromagnets

There are both advantages and disadvantages in the use of electromagnets over permanent magnets. Permanent magnets are better in some places whereas electromagnets are better in some places. Though there are several benefits of electromagnets over permanent magnets the main advantage of electromagnets over permanent magnets is that the magnetic field of the electromagnets can be controlled by changing the intensity of the flow of current and their poles can be altered by swapping the terminals of the power source.

As far as the permanent magnet concerns its magnetic field is constant without the use of source outside whereas in case of electromagnets a continuous and constant current supply is necessary to maintain the constant magnetic field. In the permanent magnets, their magnetic field decays due to continuous use and also with time so they need a recharge to get the same constant magnetic field whereas electromagnets do not have such requirements.

Advantages:

Electromagnets are very useful where the changing of poles and discontinuation of the magnetic field is necessary. A magnetic separator utilises this property of electromagnets very well. When magnetized by passing current, it attracts the iron scraps from the heap of scraps and its operator moves the scrap to another place and stops the current supply to drop them. By deploying magnetic separator, we get iron scrap.

Other advantages of electromagnets are that they are inexpensive and easy to build. They are lightweight and do not damage the test-piece which is a part of the electromagnet.

Disadvantages:

One of the disadvantages of electromagnets is that they heat up very fast and due to this heat generation lose of electrical energy is very much. A continuous power supply requires maintaining the constant magnetic field.  To get the strong magnetic field, a large number of coiling of copper wire is required which in turn, requires large space. So the electromagnets are unfit for small spaces. As the magnetic field is due to the electric current in electromagnets, short-circuit can damage the electromagnets and they can harm the operator badly.

FAQs on What Are Electromagnets

Q.1: What are electromagnets?

Answer: as the name suggests, electromagnets are magnets which are created by the electrical field. When the electric current passes through the copper coil rounded over the iron rod generates the magnetic field. The strength of the magnetic field depends on the intensity of the current passing through it. They are temporary magnets with a strong magnetic field. The field intensity can be altered by controlling the flow of electric current.

Q.2: What type of current is in use to make electromagnets?

Answer: In a DC circuit, current flows in one direction so creating a strong magnet like a permanent magnet DC should be used. In the AC circuit, electric current oscillates 50 or more times in a second depending on the frequency of the current and changing the direction of the current. This alteration causes too much heat generation which can damage the circuit. In long run, the use of AC can damage the electromagnet.

Q.3: What are the types of electromagnets?

Answer: There are three types of electromagnets, resistant, superconductors and hybrids.

  • Resistant: This type of magnet produces the magnetic field with copper wires. When copper wire twisted around a piece of iron and an electric current passes through the copper wire, the magnetic field generates. Increasing the twists of copper wires the stronger the field.
  • Superconductor magnets: Superconductive metal has zero resistance to the current flowing through it. The superconductor magnets are made using the same principle. These electromagnets use liquid nitrogen or liquid helium to bring down the temperature of the copper coil. The low temperature keeps the copper atoms away from the flow of current and gives the strong magnetic field. These electromagnets keep working even after the blockage of current.
  • Hybrid electromagnets: These magnets are the combination of above two types of electromagnets, resistant and superconductor electromagnets.
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