Examples

Examples of Electromagnetic Energy

We explain that what are the examples of electromagnetic energy? The term electromagnetic energy refers to two phenomena that are deeply linked and naturally present in our universe:

• The energy carried by the radiation that makes up the electromagnetic spectrum , from radio waves to Gamma rays.
• The energy carried by electric charges , since when passing through a conductor, in addition to existing as part of a current, they create a magnetic field; and also all the equipment that works with electricity and magnetism.

Generation of electromagnetic waves

Electromagnetic waves are generated by vibrations of electric and magnetic fields , and do not need a material medium for propagation, that is, they can travel through a vacuum. The electric field and the magnetic field are perpendicular to each other, and both are perpendicular to the direction of propagation. The speed at which they travel is that of light: C = 3 * 10 8 m / s.

The concept of electromagnetic waves has its origin in the fact that every accelerated electric charge emits energy in the form of electromagnetic radiation . To produce these waves, an oscillating circuit consisting of a coil and a capacitor can be prepared. What happens in the circuit is an exchange of energy between the capacitor and the coil.

The capacitor starts supplied with a charge (from a source, such as a battery). At the moment of starting the current, the energy is maximum in the capacitor and there is nothing in the coil. The capacitor will discharge . When it is totally discharged, the energy has been stored in the coil and the electric field between the plates of the capacitor disappears.

While current has flowed in the coil, a magnetic field has been produced. And the instant the capacitor has discharged, the current ceases, the magnetic field disappearing. This disappearance causes a current in the opposite direction that charges the capacitor again, returning to the initial conditions. And the process repeats itself. The time it takes for the cycle to complete is called the period of the circuit .

In this circuit, the electromagnetic energy is stored without radiating to the outside. This irradiation is achieved by gradually separating the armor of the condenser. By having the maximum possible separation, the energy is radiated in the form of double transverse spherical waves.

Energy in electromagnetic waves

There are four fundamental events that served as the basis in 1864 for the Scottish physicist James Clerk Maxwell, to begin the synthesis of electrical phenomena and magnetic phenomena known in his time, and their explanation within a broad theory known as the Theory of electromagnetism .

These events are the following:

• The physicist Oersted had demonstrated in 1820 the existence of magnetic effects due to electric currents .
• Faraday’s discoveries in 1831 had shown that magnetic fields varying with time give rise to a movement of electric charges in conductors.
• Faraday’s explanation of these so  called induction phenomena had introduced for the first time in the history of physics the notion of a magnetic field represented by a set of lines of force.
• In 1785, Charles Coulomb had described in law the way in which electric charges attract each other.

Maxwell began by shaping Faraday’s observations and his notion of the magnetic field into equations. In 1864, he published an article entitled “Dynamic Theory of the Electromagnetic Field”, in which he presented the famous equations that unified the electric and magnetic fields, and showed that these equations predicted the existence of waves of the electric and magnetic fields: electromagnetic waves .

Maxwell identified these electromagnetic waves with light and, therefore, his equations not only unified electric and magnetic fields, but also optical phenomena. As of today, it is established that visible light is , as is, a type of electromagnetic wave . Other examples are radio frequency waves, microwaves, X-rays, etc.

Maxwell’s discoveries had an unprecedented impact on all human activity. Although the greatest advances occurred in the 20th century and so far in the 21st, Maxwell was aware of its importance.

He wrote: “I am preparing an article with an electromagnetic theory of light, which as long as I am not convinced otherwise, I think it will be a great advance.”

The mathematical relationships between electric and magnetic fields developed by Maxwell provide a solid theoretical basis for the treatment of all electromagnetic phenomena.

Examples of electromagnetic energy

1. Radio waves, which are transmitted from radio towers and propagate through the air to receiving antennas.
2. The ovens that operate by incising microwaves on the food, so that its temperature rises.
3. Infrared radiation, emitted by hot objects and associated with thermal energy.
4. Visible light falls on objects and they reflect a portion of it. This portion tells us what color those objects are.
5. Ultraviolet rays are emitted by the sun and reach planet Earth. The earth’s atmosphere is responsible for filtering them with the ozone molecules that compose it.
6. X-rays are used in health centers, emitted towards the body of a patient. The waves pass through the meat and generate a projection of the bones on a plate.
7. Gamma rays spread through the universe, the product of reactions in bodies such as stars.
8. A squirrel cage induction motor or SCIM (Squirrel Cage Induction Motor) runs on electromagnetic energy.
9. A wound rotor induction motor or WRIM (Wired Rotor Induction Motor) runs on electromagnetic energy.
10. When ultraviolet rays strike human skin for a long time, burns appear that can lead to skin cancer.

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