Electromagnetism

Electromagnetism - Definition and Examples

Introduction: 


Electromagnetism, a science of charge and of the forces and fields related to charge. Electricity and magnetism are 2 aspects of electromagnetism.



Electricity and magnetism were long considered to be separate forces. It was not until the 19th century that they were finally considered as interrelated phenomena. In 1905 Albert Einstein’s special theory of relativity discovered beyond a doubt that both are aspects of one common phenomenon. At a practical stage, however, electric and magnetic forces behave quite differently and are characterized by differential equations. Electric forces are produced by electric charges either at the state of rest or in motion. Magnetic forces, on the other hand, are produced only by moving charges and act solely on charges which are in motion.

Electric phenomena can occur even in a neutral matter because the forces act on the individual charged constituents. The electric force, in a specific, is responsible for most of the physical and chemical properties of atoms and molecules. It is enormously strong when compared with gravity. For example, the absence of only 1 electron out of every billion molecules in 2 70-kilogram (154-pound) persons standing 2 meters (two yards) apart would repel them with a 30,000-ton force. On a more common scale, electric phenomena are responsible for the lightning and thunder accompanying certain storms.
Electric and magnetic forces can be found in regions called the electric and magnetic fields. These electric and magnetic fields are fundamental in nature and can exist in space far from the charge. The Electric fields can produce magnetic fields and vice versa, independent of any external charge. The changing magnetic field gives an electric field, as the physicist Michael Faraday discovered in work that forms the basis of the electric power generation. Conversely, a varying electric field produces a magnetic field, as the Scottish physicist James Clerk Maxwell deduced. 

The famous mathematical equation formulated by Maxwell incorporated light and wave phenomena into electromagnetism. Maxwell showed that electric and magnetic fields move together through space as waves of electromagnetic radiation, with the varying fields mutually sustaining each other.




Let us discuss an example of electromagnetic waves traveling through space independent of matter are radio and television waves, microwaves, infrared rays, visible light, UV rays, X-rays, and gamma rays. All of these electromagnetic waves travel at the same speed namely, the velocity of light. They vary from each other only in the frequency at which their electric and magnetic fields oscillate.

Maxwell’s equations still provide a full and elegant description of electromagnetism down to, but not including, the subatomic scale. The interpretation of Maxwell’s work, however, this is broadened in the 20th century. Einstein’s very special relativity theory combined electric and magnetic fields into one single field and limited the velocity of all the matter to the velocity of electromagnetic radiation. During the late 1960s, the scientist and physicists discovered that other forces in nature have fields with a mathematical structure similar to that of the electromagnetic field. 

These additional forces are a strong force, responsible for the energy released in nuclear fusion, and the weak force, observed in the radioactive decay of unstable atomic nuclei. To be specific, the weak and electromagnetic forces have been combined into a common force called the electroweak force. The goal of many physicists to unite all of the basic forces, including gravity, into one grand unified theory has not been attained to date.

Fundamentals:


In modern life is pervaded by electromagnetic waves phenomena. When we switch on the lightbulb, the current flows through a thin filament in the bulb, and the filament gets heated because of the current flow to such a high temperature that it glows, illuminating its surroundings. In the Electric clocks and connections link simple devices of this kind into complex systems such as traffic lights monitoring that are timed and synchronized with the speed of vehicular flow. The communication devices like Radio and television sets receive information carried by electromagnetic waves traveling through space at the speed of light. To start an automobile such as a motor, currents in an electric starter motor generate magnetic fields that rotate the motor shaft and drive engine pistons to compress an explosive mixture of gasoline and air; the spark which gets initiated to form the combustion is an electric discharge, which makes up a momentary current flow.

The main properties of an Electromagnet are:


(i) An electromagnet is temporary in nature.
(ii) An electromagnet is made of a soft iron core.
(iii) The magnetic field strength can be changed.
(iv) An electromagnet can be easily demagnetized by switching off the current.
(v) The polarity can be reversed.

The principle of charge conservation:


Like Coulomb’s law, the principle of charge conservation is a very fundamental law of nature. According to the principle, the charge of an isolated system (separate system) cannot change. If another positively charged particle appears within a system, a particle with a negative charge of the same magnitude (value) will be created at the same time; thus, the principle of conservation of charge is maintained. In nature, a pair of oppositely charged particles are formed when high-energy radiation interacts with matter; an electron and a positron are formed in this process known as pair production.

Electric fields and forces:


The value of the electric field at a particular point in space, for example, equals the force that would be exerted on a unit charge at a particular position in space.

Every charged body sets up an electric field in the surrounding space. A second charge can feel the presence of this field. The second charge is either attracted towards the initial charge or repelled from the charge, depending on the signs of these charges. Since the second charge also has an electric field, the first charge can feel its presence and is either attracted or repelled by the second charge also.

Magnetic fields and forces:


The magnetic force influences only on those charges that are already in motion (moment) and this is transmitted by the magnetic field. Both the magnetic fields and magnetic forces are more complicated to understand than electric fields and electric forces. The magnetic field doesn't point along the direction of the source of the field; rather, it points in a perpendicular direction. In addition, the magnetic force acts in a direction that is perpendicular to the direction of the magnetic field. In comparison, with both the electric force and the electric field which points directly towards or away from the charge.