An Introduction to Magnetism, Electromagnetism and Electromagnetic Induction
In today's world, we use magnets for many different tasks. From refrigerator doors to headphones, power generation and transportation to car engines. They all use magnetic force in one way or another.
Thanks to the current ubiquity of magnets, our society would be pretty much lost without them. For example, we would not be able to transport electrical currents across the country. Our electric motors would all be useless. It would also no longer be possible to communicate over long distances, which is now unimaginable.
For these reasons, we should not take these small objects for granted. Rather, all of us, not just scientists, should try to understand them: how they work, what constitutes the special relationship between electricity and magnetism, and how they power the world.
This is also our goal for this series of articles: that everyone can understand why electrons have a magnetic moment or why an electric current can produce a magnetic field. Why magnetic flux can cause electrical voltage or why all this is so important for our world.
So let's take a look at all this in a little digression on physics tutoring, from the basics of magnetic fields to the most important magnetic technologies.
What is magnetism?
Let's start with magnetism.
Magnetism is a force present in and between objects that is created by the movement of electrons and results in the attraction and repulsion of different objects. It is a non-contact force that influences every single object in the world to a greater or lesser extent and is based on the movements of subatomic particles, electrons and their electric charge.
Electrons, magnetic moment and the three types of magnets
Each atom of a substance is made up of particles such as neutrons, electrons, and protons. Electrons are mainly responsible for magnetism.
They tend to orbit the neutrons and are all differently charged, either positive or negative. Generally speaking, oppositely charged electrons pair with each other, so a negatively charged electron pairs with a positive one, which neutralizes the respective charges and makes the substance relatively stable.
When substances consist only of paired electrons, we call this diamagnetism.
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However, there are numerous substances, including oxygen, that have unpaired electrons. In this case, the substance becomes much more magnetic, because its electrons align in the same direction. In most such materials, however, this does not happen, because unless an external magnetic field influences the substance, the magnetic moments of the individual electrons remain different.
These substances only behave magnetically when they are in the area of action of an external magnetic field and are called paramagnets.
Then there are ferromagnetic substances. These are magnetic substances that have unpaired electrons of the same magnetic moment. This means that they spontaneously become magnetic and remain so even in the absence of an external magnetic field.
But what is a magnetic field anyway?
Every magnet and every magnetic object has a magnetic field, the direct environment of the object in which the magnetic force acts. This area is created by the magnetic charge of the magnet.
Permanent magnets and electromagnets have continuous magnetic fields, the structure of which is best observed by using iron filings. These magnetic field lines flow from the north pole of the magnet to the south pole.
Magnetic fields differ depending on the strength of the magnet.
What is an electromagnet?
In addition to the magnetic moment of electrons, magnetic fields are also created by electrical voltage. This discovery dates back to the 1830s and is considered one of the most important discoveries in history, as it was the first to combine magnetism with electricity.
As explained earlier, electrons of a substance have a magnetic charge, depending on their movement within the magnetic substance.
But where electrons really move is in electric currents, which in turn are merely moving electrons. So when currents flow along a wire, the wire is magnetized because the movement of the electrons generates a magnetic field.
The whole thing was discovered by the namesake of the unit Ampere, André-Marie Ampère, when he was able to show that parallel wires attracted or repelled each other, depending on the direction of the current.
How is an electromagnet constructed?
Since the beginnings of electromagnetism, the technology has not changed much. They have become stronger, but the basic structure of the devices has remained the same.
Electromagnets consist of a coil of wire wrapped around a metal core, most often a ferromagnet such as iron. An electric current is chased through the wire coil, whose magnetic field is directed towards the center of the coil, i.e. into the iron core. This structure is also called a solenoid and is still used today wherever electromagnets are used.
As soon as the electric current is switched off, the solenoid also loses its magnetic power.
A Note on the Link Between Magnetism and Electricity
We know that electricity produces a magnetic field and magnetic fields are based on electrons, but the distinction between a domain of magnetism and a separate domain of electricity is inconclusive.
The two forces can hardly be separated from each other. Rather, they form a physical principle, two sides of the same coin. "Electromagnetism" is thus one of the fundamental forces of the universe.
What is electromagnetic induction?
One of the most important discoveries in the history of electromagnetism can be traced back to Michael Faraday, a British scientist of the 19th century. It is called electromagnetic induction and still forms the basis of our knowledge of electromagnets today.
Faraday's experiments dealt with how electric currents can be influenced by magnetic fields. He found that changes in the magnetic field can be used to produce an electric current.
This sounds complicated, but the actual experiments were pretty simple. Faraday took an iron ring and wound two different wires around the opposite sides of the ring, creating two solenoids on the same piece of iron.
He connected one wire to a battery and the other to a galvanometer, a device for measuring electrical voltage. When he ran current from the battery through the first wire and switched it off again, the voltage measured by the galvanometer changed. For Faraday, this was proof that a change in the magnetic field of the iron ring can cause an electric current in a separate wire.
In order to prove his thoughts on the relationship between electricity and magnetism more concretely, he conducted another experiment. He took a solenoid without an iron core (i.e. simply a coil of wire) and inserted and removed a bar magnet. The faster he moved the magnet into the coil, the stronger the current produced in the wire became.
Why was that so exciting? Faraday was thus able to show that electric currents do not only flow through wire and create the theoretical basis that enables us today to produce electrical energy by manipulating magnetic fields.
What is a transformer?
Transformers are essential devices that make use of the principles of electromagnetic induction.
They are perhaps the most abundant electrical appliances on the planet, after all, almost all of the electrical energy we produce and consume passes through a transformer at least once in its life cycle.
So, what is a transformer? A transformer is a static device that changes high-voltage current to low-voltage current. This is done by two adjacent solenoids and with the help of Faraday's electromagnetic induction.
Electricity is transported throughout the country via huge power grids. To reduce the cost of this, the electricity is transported at super high voltage. In contrast to high current, this avoids wasting energy and uses smaller cables.
However, high-voltage electricity is not at all suitable for private use. So before electricity is distributed locally in our homes, it must be transformed into low-voltage electricity. This task is performed by transformers.
Reduce voltage
Faraday's Law shows how electromagnetic induction can be used to reduce or increase the voltage of electric currents.
Remember his experiment: He took two different wires and was able to generate an electric current in the second wire by changing the magnetic field of the two.
However, if you were to change the number of turns in the wire, you could change the voltage of the current generated. So if you had ten turns in the first wire, you could take half of them in the second wire and thus create half of the voltage.
That's exactly how transformers work!
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