What is Electromagnetism:
Electromagnetism is the study of charges and the interaction between electricity and magnetism. Electricity and magnetism are aspects of a single physical phenomenon closely linked by the movement and attraction of charges in matter.
The branch of physics that studies the interaction between electrical and magnetic phenomena is also known as electromagnetism.
The word "electricity" was proposed by the Englishman William Gilbert (1544-1603) from the Greek elektron (a kind of amber that attracts objects when rubbed with various substances). On the other hand, "magnetism" probably arose from a Turkish region with deposits of magnetized magnetite (Magnesia), where an ancient Greek tribe known as the Magnetes lived.
However, it was until 1820 that Hans Christian Oersted (1777-1851) succeeded in demonstrating the effect of an electric current on the behavior of a compass, thus the study of electromagnetism was born.
Magnets and electricity have always been the subject of fascination for mankind. His initial approach took different courses that reached a meeting point at the end of the 19th century. In order to understand what electromagnetism is all about, let's review some basic concepts.
Electric charge is a fundamental property of the particles that make up matter. The basis of all electric charges resides in the atomic structure. The atom concentrates positive protons in the nucleus, and negative electrons move around the nucleus. When the number of electrons and protons is equal, we have an atom with a neutral charge. When the atom gains an electron it is left with a negative charge (anion), and when it loses an electron it is left with a positive charge (cation).
Then the charge of the electron is considered as the basic unit or quanta of the electric charge. This is equivalent to 1.60 x 10 -19 coulomb (C), which is the unit of measurement for charges, in honor of the French physicist Charles Augustin de Coulomb.
Electric field and magnetic field
An electric field is a field of force that surrounds a charge or charged particle. That is, a charged particle affects or exerts a force on another charged particle that is in the vicinity. The electric field is a vector quantity represented by the letter E whose units are volt per meter (V / m) or newton per coulomb (N / C).
On the other hand, the magnetic field is produced when there is a flow or movement of charges (an electric current). We can say then that it is the region where the magnetic forces act. Thus, an electric field surrounds any charged particle, and the movement of the charged particle creates a magnetic field.
Each moving electron produces a tiny magnetic field in the atom. For most materials, electrons move in different directions so the magnetic fields cancel out. In some elements, such as iron, nickel, and cobalt, the electrons move in a preferential direction, producing a net magnetic field. Materials of this type are called ferromagnetic.
Magnets and electromagnets
A magnet is the result of the permanent alignment of the magnetic fields of the atoms in a piece of iron. In an ordinary piece of iron (or other ferromagnetic material) the magnetic fields are randomly oriented, so it does not act like a magnet. The key feature of magnets is that they have two poles: north and south.
An electromagnet consists of a piece of iron inside a coil of wire through which a current can be passed. When the current is on, the magnetic fields from each atom that make up the piece of iron align with the magnetic field produced by the current in the coil of wire, increasing the magnetic force.
Electromagnetic induction, discovered by Joseph Henry (1797-1878) and Michael Faraday (1791-1867), is the production of electricity by means of a moving magnetic field. By passing a magnetic field through a coil of wire or other conductive material, a flow of charge or current is caused when the circuit is closed.
Electromagnetic induction is the basis of generators and practically of all electrical power produced in the world.
Applications of electromagnetism
Electromagnetism is the basis of the operation of electrical and electronic devices that we use daily.
Microphones have a thin membrane that vibrates in response to sound. Attached to the membrane is a coil of wire that is part of a magnet and moves alongside the membrane. The movement of the coil through the magnetic field converts sound waves into electrical current that is transferred to a speaker and amplified.
Generators use mechanical energy to produce electrical energy. Mechanical energy can come from water vapor, created by burning fossil fuels, or from falling water in hydroelectric plants.
A motor uses electrical energy to produce mechanical energy. Induction motors use alternating current to convert electrical energy into mechanical energy. These are the motors typically used in household appliances, such as fans, dryers, washers, and blenders.
An induction motor consists of a rotating part (rotor) and a stationary part (stator). The rotor is an iron cylinder with grooves along which copper fins or bars are attached. The rotor is enclosed in a container of coils or turns of conductive wire through which alternating current is passed, becoming electromagnets.
The passage of alternating current through the coils produces a magnetic field that in turn induces a current and a magnetic field in the rotor. The interaction of magnetic fields in the stator and rotor causes a torsion in the rotor allowing work to be done.
Maglev: trains that levitate
Magnetically levitated trains use electromagnetism to lift, guide and propel themselves on a special track. Japan and Germany are pioneers in the use of these trains as a means of transport. There are two technologies: electromagnetic suspension and electrodynamic suspension.
The electromagnetic suspension is based on the attractive forces between powerful electromagnets at the base of the train and the railroad track. The magnetic force is adjusted so that the train remains suspended over the track, while it is driven by a magnetic field that travels forward by interaction of lateral magnets in the train.
Electrodynamic suspension is based on the repulsive force between magnets in the train and an induced magnetic field on the railroad. This type of train needs wheels to be able to reach a critical speed, similar to airplanes when they are about to take off.
Magnetic resonance imaging is one of the technologies with the greatest impact in modern medicine. It is based on the effect of strong magnetic fields on the hydrogen nuclei of the body's water.
Many of the electromagnetic phenomena that we know are a consequence of the Earth's magnetic field. This field is generated by electrical currents inside the planet. The Earth then resembles a large magnetic bar within it, where the magnetic north pole is at the geographic south pole and the magnetic south pole corresponds to the geographic north pole.
The compass is an instrument dating from approximately 200 years before Christ.It is based on the orientation of a magnetized metal needle towards the geographic north.
Some animals and other living things can detect the Earth's magnetic field and thus orient themselves in space. One of the targeting strategies is through specialized cells or organs that contain crystals of magnetite, an iron oxide mineral that maintains a permanent magnetic field.
The northern and southern auroras
The Earth's magnetic field works as a protective barrier against the bombardment of high-energy ionized particles emanating from the Sun (better known as the solar wind). These are diverted to the polar regions, exciting atoms and molecules in the atmosphere. The characteristic lights of the auroras (boreal in the northern hemisphere and austral in the southern hemisphere) are the product of the emanation of energy when the excited electrons return to their basal state.
Maxwell and the theory of electromagnetism
James Clerk Maxwell deduced between 1864 and 1873 the mathematical equations that explain the nature of magnetic and electric fields. In this way, Maxwell's equations provided an explanation of the properties of electricity and magnetism. Specifically, these equations show:
- how an electric charge produces an electric field,
- how currents produce magnetic fields, and
- how changing a magnetic field produces an electric field.
Maxwell's wave equations also served to show that changing an electric field creates a self-propagating electromagnetic wave with electric and magnetic components. Maxwell's work unified the seemingly separate areas of physics of electricity, magnetism, and light.