Tag Archives: electromagnetic field

Electromagnetism and the Modern Age

If one had to rate the greatest discoveries of all time, electricity would rank high on any list. Most of the modern world is powered by electricity. What would our lives be like without electricity? Just think of your own home; when the power goes out everything gets put on hold. Take people’s smart phones away and they don’t know what to do with themselves.

The application of electricity was the result of 3 centuries of investigation and experiments into the nature of electricity and magnetism. Understanding the relationship between the two forces and unifying them into a single force, called electromagnetism, proved to be a critical step. The unification of electricity and magnetism also established the existence of electromagnetic waves, the fundamental principle behind wireless technology.

Fascination and Curiosity

In the 1700s static electricity was a well-known phenomenon, and various devices were made to produce it. Electricity was poorly understood at first. Its main use was as an entertainment tool as it could create colorful sparks and move small objects. It was used in types of magic shows that were meant to delight crowds.

Over time the curious nature of electricity demanded an explanation, and a number of experimenters tried to find out. Where did electricity come from? Static electricity was observed to pass through people. Some animals were known to produce electric shocks. Therefore, was electricity intrinsic to life itself or were the living bodies a medium for carrying a fundamental force of nature?

In 1799, Alessandro Volta, an Italian physicist and chemist showed that electricity could be generated artificially. He created the first battery by piling up metal plates, separated by cards dipped in dilute acid, and attaching both ends to wires. Metals have a unique quality where at the atomic level the electrons in the outer shells can be shared. Under the right conditions the electrons can flow from one atom to another. This produces an electric current.

The unit for measuring electric potential is named in Volta’s honor (the volt). Up until Volta’s pile, as it was called, electricity could only last for an instant. Now it could be stored in a battery, which opened the door for electricity to do useful work. But the road¬†of inventing electrical technologies would be long and winding. The knowledge of electricity was still in its infancy.

The Insights of Faraday and Maxwell

Michael Faraday was a self-educated scientist, who is famous for his experiments with electricity and magnetism. His work would lead to unlocking the secrets of the two mysterious forces. Faraday picked up the work of Danish physicist, Hans Christian Orsted. In 1820, Orsted accidentally discovered that a current carrying wire caused a nearby magnetic needle to move. In other words, an electric field created a magnetic field.

Knowing that an electric current had an effect on magnets at a close distance; Faraday wondered if the experiment could be reversed. Could magnets generate electricity? Faraday set out to explore the relationship further, and in 1831 he discovered that a changing magnetic field caused an electric current in a nearby wire. The key insight was that electricity was produced when the magnetic field changed as it interacted with the wire. A stationary magnetic field and a wire did not induce a current. Therefore, a third variable was needed – motion. The motion of a magnetic field in relation to a wire generated the electricity.

This principle, known as electromagnetic induction, is responsible for powering all electric motors and generators. Electric power is generated by a changing magnetic field and its interaction with a coil of wire. The coil multiplies the amount of power generated, but operates under the same principle as Faraday’s experiment with a single wire.

Three decades later a Scottish physicist by the name of James Clerk Maxwell¬†put the finishing touch on the unification of electricity and magnetism. By the time Maxwell came along it was well-established that there existed a connection between the two forces. The telegraph had been invented, the first long-distance communication device, which operated on the principle of electromagnetism. Maxwell’s great achievement came in 1862; he devised 4 simple equations that represented all the interactions between electricity and magnetism.

The original concept of two distinct forces was united under one theoretical framework. Electromagnetism became known as one of the 4 fundamental forces of nature recognized by modern physics; the other 3 being, the strong nuclear force, weak nuclear force and gravity. In short, Faraday unified electricity and magnetism experimentally, and Maxwell unified them mathematically.

Fields, Waves and Light

With Maxwell’s equations came a new understanding of electromagnetism. Not only were the two forces unified, but the concepts of fields and waves would become extremely important. Modern physics would be transformed by the knowledge that energies could occupy regions of space and have noticeable effects. In This Explains Everything, physicist Lawrence Krauss writes:

“[Maxwell’s equations] established the physical reality of what was otherwise a figment of Faraday’s imagination: a field – that is, some quantity associated with every point in space and time.”

Maxwell realized that if a changing electric field created a magnetic field, and a changing magnetic field created an electric field, then the process would be continuous (a kind of chain reaction). The mutual interaction of electricity and magnetism would cause the field to oscillate. When an electromagnetic field oscillates it generates an electromagnetic wave, which has an independent existence and moves out from the source. Maxwell was able to calculate the speed at which electromagnetic waves propagate. It tuned out it was precisely the speed of light. Krauss writes about Maxwell’s conclusion:

“Thus he discovered that light is indeed a wave – but a wave of electric and magnetic fields that moves through space at a precise speed…”

Maxwell’s discovery of a constant speed of light was the starting point for Einstein’s revision of space and time – the theory of special relativity. A decade later Einstein formulated the theory of general relativity. It was then followed by quantum theory, and the age of modern physics was in full swing.

A World Beyond Imagination

The scientists and inventors of the 1700s and 1800s could not have imagined the modern world that resulted from their work. Electricity and information technology could not have been possible if not for a complete understanding of electromagnetism. It was the start of something big, and step by step new discoveries and inventions pushed the boundaries of progress. Many innovators took part in the quest. Our world has become brighter, smaller and faster.

I know I am dating myself; however, I grew up watching a black and white television. At first the TV only aired 2 channels, of which the signal was received by an antenna in the attic. There was no remote control back then, so we had to manually turn the dial to change the channel. In addition, someone had to walk up to the attic and turn the antenna around. Eventually, we upgraded by adding a second antenna (each pointing in a different direction) and running wires to a switch besides the TV. I guess that was progress back then. Nowadays people complain if the Wi-Fi is slow.

I am amazed at all the electronic gadgets we have today, and all they can do. They work on principles that take advantage of things we can’t even see. How can electrons moving through wires light our homes and power computers? How can waves traveling through space carry information that can be converted to video and audio? Plus, most of the time, the signal is perfectly clear. When I consider that it took 3 centuries of inventions to get to this point, I am not going to get upset over a slow WiFi; I am just grateful it works at all.

 

References: Edge Foundation Inc., This Explains Everything (New York: HarperCollins Publishers, 2013), 335, 336.

In Our Time: Science, Michael Faraday, Dec. 24, 2015.

In Our Time: Science, The Invention of Radio, July 3, 2013.

In Our Time: Science, Maxwell, Oct 1, 2003

Shock and Awe: The Story of Electricity — Jim Al-Khalili BBC Horizon, Published on May 26, 2015.


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