Hola! I'm Alexa Guido, a young and curious woman passionate about science. Join me on an exciting journey to explore the wonders of the universe through the lens of physics.
Among the four fundamental forces of the universe, electromagnetism stands out as the most tangible and intuitive force in our everyday lives. It’s the only force we can manipulate on a human scale, and without it, our modern lives would be unimaginable. Think about it; how else could you cook your favorite meal in the microwave, snap an X-ray, or even bask in the warmth of the Sun?
Electromagnetism is the beautiful union of magnetism and electricity, which can be fully described with 4 elegant and simple equations. At the atomic scale, it controls the interactions between each molecule and atom, forming the very foundation of the periodic table and giving rise to all of the known fundaments of chemistry. Moreover, it is the force that ties atoms together into solids and liquids and is responsible for the incredible range of properties that different materials have.
When we zoom out to the macroscopic scale, electromagnetism personifies itself in the familiar phenomena that give the force its name. In the case of electricity, this means everything from rubbing a balloon on your head and sticking it on the wall to plugging any device and being pretty confident that it will work. On the magnetic side, consider the charming magnets on your fridge door through to the gigantic trains in Japan that levitate effortlessly above the rails.
As if this wasn’t enough, electromagnetism, quite literally, is responsible for everything you’ve ever seen. It is the force that gives rise to light itself in a tiny piece of the electromagnetic spectrum.
So, why did it take until the 19th century for scientists to connect electricity and magnetism? At a practical level, electric and magnetic forces behave quite differently and are described by different equations: electric forces arise from stationary or moving charges, while magnetic forces come into play only with moving charges.
However, both electric and magnetic forces can be detected in their respective fields—electric and magnetic fields—which are fundamental aspects of nature and can exist far from the source that created them. Interestingly, electric fields can generate magnetic fields and vice versa!
In 1873, James Clerk Maxwell published four groundbreaking equations that unified light and wave phenomena into a single one, electromagnetism. He showed that electric and magnetic fields travel together through space as waves of electromagnetic radiation, with each field supporting the other. In other words, there is as much energy carried by the electric component of the wave as by the magnetic component, and the energy is proportional to the square of the field strength as well.
Fast forward to the 20th century, Einstein’s special relativity theory connected electric and magnetic fields into one common field and established that no matter can exceed the speed of electromagnetic radiation, our beloved speed of light.
Whereas, in terms of the modern quantum theory, electromagnetic radiation is the flow of photons through space in packets of energy (hν), all traveling at the universal speed of light. The electron volt (eV) has become the standard unit of energy, which is the energy that can be given to an electron by a one-volt battery.
These photons can also be seen as the spectrum of frequencies of electromagnetic radiation. Stretching from the lower end with gigantic radio waves and microwaves, through visible light, and soaring up to the high-energy realms of ultraviolet light, X-rays, and gamma rays emitted by cosmic events like supernovas.
The speed of all forms of electromagnetic radiation is a constant defined as exactly c = 299,792,458 meters per second. The energy produced by this radiation comes from charged particles, which means that the particle loses energy in the process.
Each particle in the Universe carries with it several properties that determine how the particle interacts with each of the four fundamental forces. For instance, the force of gravity is mass. For the force of electromagnetism, the key property is called electric charge. This fundamental aspect of matter, carried by elementary particles, determines how they respond to electric and magnetic fields. Indeed, all electrically charged objects have an electric field around them.
There are two types of electrical charge: positive and negative. In an electric field, a charged particle, or charged object, experiences a force. If the forces acting on any object are unbalanced, it will cause the object to accelerate, influenced by the dominant electric field.
With this in mind, if you bring two objects with the same charge close together, they will repel each other, while two objects with opposite charges will attract one another. This basic principle is at the heart of many phenomena we observe in nature.
Finally, one of the cornerstone principles of electromagnetism is Coulomb’s law, formulated by the 18th-century French physicist Charles-Augustin de Coulomb. This law describes the electric force between charged objects and is similar to Newton’s law of gravitation. Both gravitational and electric forces diminish with the square of the distance between the objects and act along the line connecting them.
In terms of units, the SI system defines the electric charge unit as the coulomb, and the electron carries a negative charge of approximately 1.602176634 × 10^(-19) coulombs. From the unseen forces that govern the subatomic world to the everyday phenomena that shape our lives, electromagnetism is truly a remarkable force that connects us all.
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