# electromagnetism

2022

We explain what electromagnetism is and what are some of its applications. Also, its history and examples.

Electromagnetism studies the relationship between electrical and magnetic phenomena.

## What is electromagnetism?

Electromagnetism is the branch of thephysical that studies the relationships between electrical and magnetic phenomena, that is, the interactions between particles loaded and electric fields Y magnetic.

In 1821 the foundations of electromagnetism were made known with the scientific work of the British Michael Faraday, which gave rise to this discipline. In 1865 the Scotsman James Clerk Maxwell formulated the four "Maxwell equations" that completely describe electromagnetic phenomena.

## Applications of electromagnetism

Compasses work by electromagnetism.

Electromagnetic phenomena have very important applications in disciplines such as engineering,electronics, theHealth, aeronautics or civil construction, among others. They appear in everyday life, almost without realizing it, in compasses, speakers, doorbells, magnetic cards, hard drives.

The main applications of electromagnetism are used in:

## Experiments on electromagnetism

Through simple experiments it is possible to understand some electromagnetic phenomena, such as:

The electric motor. To carry out an experiment that shows a basic notion of how an electric motor works, we need:

• A magnet
• A battery AAA
• A screw
• A piece of electrical cable 20 cm long
• First step. Rest the tip of the screw on the negative pole of the battery and rest the magnet on the head of the screw. You can see how the elements attract each other due to the magnetism.
• Second step. Join the ends of the cable with the positive pole of the battery and with the magnet (which is together with the screw, on the negative pole of the battery).
• Result. The battery-screw-magnet-cable circuit is obtained through which a electric current that passes through the magnetic field created by the magnet, and it rotates at high speed due to a force tangential constant called "Lorentz force". On the contrary, if you try to join the pieces by reversing the poles of the battery, the elements repel each other.

Faraday's cage. Below is a detailed experiment that allows to understand how electromagnetic waves flow in electronic devices. For that, the following items are needed:

• A battery-operated portable radio or cell phone
• A metal grid with holes no larger than 1 cm
• Pliers or scissors to cut the grid
• Small pieces of wire to attach the wire mesh
• Aluminum foil (may not be necessary)
• First step. Cut a rectangular piece of wire mesh 20 cm high by 80 cm long, so that a cylinder can be assembled.
• Second step. Cut another circular piece of wire mesh 25 cm in diameter (it should have a sufficient diameter to cover the cylinder).
• Third step. Join the ends of the rectangle of the metal grid so that a cylinder is formed and fasten the ends with pieces of wire.
• Fourth step. Place the switched on radio inside the metal cylinder and cover the cylinder with the metal grid circle.
• Result. The radio will stop playing because electromagnetic waves from outside cannot pass through the metal.
If instead of a radio on, a cell phone is inserted and that number is called to make it ring, it will happen that it will not ring. In the event that it rings, you should use a thicker metal grill and smaller holes, or wrap the cell phone in aluminum foil. Something similar happens when talking on the cell phone and entering an elevator, causing the signal to cut is the effect of the "Faraday cage".

## What is electromagnetism for?

Electromagnetism allows the use of devices such as microwaves or television.

Electromagnetism is very useful for the human being since there are countless applications that allow you to meet your needs. Many instruments that are used on a daily basis work due to electromagnetic effects. The electrical current that circulates through all the connectors in a house, for example, provides multiple uses (the microwave oven, the fan, the blender, the TV, thecomputer) that work due to electromagnetism.

## Magnetism and electromagnetism

Magnetism is the phenomenon that explains the force of attraction or repulsion between magnetic materials and moving charges.

Electromagnetism involvesphysical phenomena produced by electrical charges at rest or inmovement, which give rise to electric, magnetic or electromagnetic fields, and which affect matter that may be in agaseous, liquid Ysolid.

## Examples of electromagnetism

The doorbell works through an electromagnet that receives an electrical charge.

There are numerous examples of electromagnetism and among the most common are:

• The ringer. It is a device capable of generating a sound signal when pressing a switch. It works through an electromagnet that receives aelectric charge, which generates a magnetic field (a magnet effect) that attracts a small hammer that impacts against the metal surface and emits asound.
• The magnetic levitation train. Unlike the train driven by an electric locomotive that travels on rails, this is a means of transport that is sustained and propelled by the force of magnetism and by the powerful electromagnets located in its lower part.
• The electrical transformer. It is an electrical device that allows you to increase or decrease thevoltage (or the voltage) of an alternating current.
• The electric motor. It is a device that converts theelectric power in mechanical energy, producing movement by action of the magnetic fields that are generated inside.
• The dynamo. It is an electrical generator that uses the mechanical energy of a rotating movement and transforms it into electrical energy.
• The microwave. It is an electric oven that generates electromagnetic radiation at the frequency of microwaves. These radiations vibrate the molecules fromWater that possess the food, which produces heat quickly, cooking food.
• Magnetic resonance imaging. It is a medical test through which images of the structure and composition of an organism are obtained. It consists of the interaction of a magnetic field created by a machine, the magnetic resonator, (which works like a magnet), and theatoms of hydrogen contained in the body of the person. These atoms are attracted by the "magnet effect" of the device and generate an electromagnetic field that is captured and represented in images.
• The microphone. It is a device that detects the acoustic energy (sound) and transforms it into electrical energy. It does so through a membrane (or diaphragm) that is attracted by a magnet within a magnetic field and that produces an electric current that is proportional to the sound received.
• Planet Earth. Our planet works like a giant magnet due to the magnetic field that is generated in its core (made up of metals such as iron, nickel). Movement ofEarth's rotation generates a stream of charged particles (the electrons of the atoms of the Earth's nucleus). This current produces a magnetic field that extends several kilometers above the surface of the planet and that repels harmful solar radiation.

## History of electromagnetism

• 600 BC The Greek Thales of Miletus observed that when rubbing a piece of amber, it was charged and was able to attract pieces of straw or feathers.
• 1820. The Danish Hans Christian Oersted carried out an experiment that for the first time united the phenomena of electricity and magnetism. It consisted of bringing a magnetized needle close to a conductor through which an electric current circulated. The needle moved in a way that evidenced the presence of a magnetic field in the conductor.
• 1826. The Frenchman André-Marie Ampère developed the theory that explains the interaction between electricity and magnetism, called “electrodynamics”. In addition, he was the first to name electric current as such and to measure the intensity of its flow.
• 1831. The British physicist and chemist, Michael Faraday, discovered the laws of electrolysis and electromagnetic induction.
• 1865. Scotsman James Clerk Maxwell introduced the fundamentals of electromagnetism by formulating the four "Maxwell equations" that describe electromagnetic phenomena.
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