Electromagnetism, Physics tutorial

Introduction to Electromagnetism:

Electromagnetism is the branch of physics that basically deals with electricity and magnetism and the interaction between them. This was first discovered in the nineteenth century and consists of extensive application in today's world of physics.

Electromagnetism is fundamentally the science of electromagnetic fields. The electromagnetic field is the field generated by objects which are charged electrically. The Radio waves, infrared waves, Ultraviolet waves and x-rays are all electromagnetic fields in a specific range of frequency. The electricity is generated by the changing of magnetic field. The phenomenon is as well termed as 'Electromagnetic induction'. Similarly the magnetic field is produced via the motion of electric charges.

The fundamental law of electromagnetism is termed as 'Faraday's law of Induction'. The phenomenon of electromagnetism was introduced in the nineteenth century, and this led to the discovery of the special theory of relativity introduced by Albert Einstein. According to his theory, electric and magnetic fields could be transformed into one other by a relative motion. This concept and its applications were discovered for the reason that many contributions from great scientists and physicists like Michael Faraday, Oliver Heaviside, James Clerk Maxwell, and Heinrich Hertz. In the year 1802, an Italian scholar explained the relationship between electricity and magnetism through deflecting a magnetic needle by means of electrostatic charges.

Electromagnetism is fundamentally a conjecture of a combined expression of an underlying force, termed as 'electromagnetic force'. The force can be observed whenever an electric charge is moving. This movement generates magnetism. The idea was coined by James Clerk Maxwell who published the theory of electricity and magnetism in the year 1865. On the basis of his theory numerous applications and other effects were discovered by other scientists. Electromagnetism has been expanded to the area of quantum physics and also where light propagates as a wave and relates as a particle.

Coulomb's law:

Most of the devices and phenomena are complicated; however they derive from the similar basic laws of electromagnetism. One of the most significant of these is the Coulomb's law that explains the electric force between the charged objects. This theory was formulated in the 18th-century by French physicist Charles-Augustin de Coulomb, it is analogous to Newton's law for the gravitational force. Both the gravitational and electric forces reduce with the square of the distance between the objects, and both the forces act all along a line between them. In Coulomb's law, though, the magnitude and sign of the electric force are finding out by the charge, instead of the mass, of an object. Therefore, charge finds out how electromagnetism affects the motion of charged objects. (Charge is the fundamental property of matter. Each and every component of matter consists of an electric charge having a value which can be negative, positive or zero. For illustration: electrons are negatively charged and atomic nuclei are positively charged. Most of the bulk matter consists of an equivalent amount of negative and positive charge and therefore has zero net charge.)

According to Coulomb, the electric force for charges at rest consists of the given properties:

1) Like charges repel one other while unlike charges attract. Therefore, the two negative charges repel one other; whereas a positive charge attracts a negative charge.

2) The repulsion or attraction acts all along the line between the two charges.

3) The size of the force differs inversely as the square of the distance among the two charges. Thus, when the distance between the two charges is twice, the repulsion or attraction becomes weaker, reducing to one-fourth of the original value. When the charges come ten times closer, then the size of the force rises by a factor of 100.

4) The size of the force is proportional to the value of each and every charge. The unit employed to measure the charge is the coulomb (C). When there were two positive charges, one of 0.1 coulomb and the second of 0.2 coulomb, they would repel one other by a force which based on the product 0.2 × 0.1. When each of the charges was decreased by one-half, the repulsion would be decreased to one-quarter of its former value.

Principle of charge conservation:

Similar to Coulomb's law, the principle of charge conservation is a basic law of nature. According to this principle, the charge of an isolated system can't change. Whenever an additional positively charged particle comes out in a system, a particle having a negative charge of the similar magnitude will be created at similar time; therefore, the principle of conservation of charge is maintained. In nature, a pair of oppositely charged particles is made if high-energy radiation interacts by matter; an electron and a positron are made in a procedure termed as pair production.

The smallest subdivision of the amount of charge which a particle can have is the charge of one proton, +1.602 × 10-19 coulomb. The electron consists of a charge of the similar magnitude however opposite sign - that is, -1.602 × 10-19 coulomb. An ordinary flashlight battery delivers a current which gives a net charge flow of around 5,000 coulomb that corresponds to more than 1022 electrons, prior to it is exhausted.

Electric current is the measurement of the flow of charge, as, for illustration, charge flowing via a wire. The size of the current is measured in amperes and represented by 'i'. An ampere of current symbolizes the passage of one coulomb of charge per second, or 6.2 billion electrons (6.2 × 1018 electrons) per second. A current is positive if it is in the direction of the flow of positive charges; its direction is opposite to the flow of the negative charges.

Electric fields and forces:

The force and conservation laws are merely two features of electromagnetism, though. Electric and magnetic forces are mainly caused due to electromagnetic fields. The word field represents a property of space, in such a way that the field quantity consists of a numerical value at each point of space. These values might as well differ with time. The value of the electric or magnetic field is a vector, that is, a quantity having both magnitude and direction. The value of the electric fields at a point in space, for illustration, equivalents the force that would be applied on a unit charge at that place in space.

Each and every charged object sets up an electric field in the surrounding space. The second charge feels the presence of this field. The second charge is either attracted in the direction of the initial charge or repelled from it, based on the signs of the charges. Obviously, as the second charge as well consists of an electric field, the first charge feels its presence and is either attracted or repelled through the second charge, too.

The electric field from a charge is directed away from the charge if the charge is positive and in the direction of charge if it is negative.

Magnetic fields and forces:

The magnetic force affects only such charges which are already in motion. This is transmitted through the magnetic field. Both the magnetic fields and magnetic forces are more complex than the electric fields and electric forces. The magnetic field doesn't point all along the direction of the source of the field; rather, it points in the perpendicular direction. Moreover, the magnetic force acts in a direction which is perpendicular to the direction of the field. In assessment, both the electric force and the electric field point directly toward or away from the charge.

A few materials, like silver, copper and aluminum, are conductors which let charge to flow freely from place to place. When an external influence establishes a current in the conductor, the current produces a magnetic field. For a long straight wire, the magnetic field consists of a direction which encircles the wire on a plane perpendicular to the wire. The strength of magnetic field reduces by distance from the wire.

Interaction of a magnetic field by a charge:

Based on the initial orientation of the particle velocity to the magnetic field, charges encompassing a constant speed in the uniform magnetic field will obey a circular or helical path.

Electric currents in the wires are not merely the source of magnetic fields. Naturally occurring minerals show magnetic properties and encompass magnetic fields. Such magnetic fields result from the motion of electrons in the atoms of the material. They as well outcome from the property of electrons termed as the magnetic dipole moment that is associated to the intrinsic spin of individual electrons. In most of the materials, little or no field is noticed outside the matter due to the reason of the random orientation of the different constituent atoms. In a few materials like iron, though, atoms in certain distances tend to become aligned in one specific direction.

Magnets encompass many applications, ranging from the use as toys and paper holders on home refrigerators to necessary components in electric generators and machines which can accelerate particles to speeds approaching that of light. The practical application of magnetism in technology is to a great extent improved by employing iron and other ferromagnetic materials having electric currents in devices such as motors. Such materials intensify the magnetic field generated by the currents and thus make more powerful fields.

Effects of varying magnetic fields:

The combination of electricity and magnetism from different phenomena into electromagnetism is tied to three closely associated events. The first was Hans Christian Ørsted's accidental discovery of the affect of an electric current on a magnetic needle namely, that magnetic fields are generated through electric currents. Ørsted's in the year 1820 report of his inspection spurred an intense effort through scientists to confirm that magnetic fields can induce currents. The second incident was Faraday's experimental proof that a changing magnetic field can induce a current in the circuit. The third was Maxwell's prediction that a changing electric field consists of an allied magnetic field. The technological revolution attributed to the growth of electric power and radio communications can be outlined to such three landmarks.

Effects of varying electric fields:

The prediction of Maxwell's that a changing electric field produces a magnetic field was a masterstroke of pure theory. The Maxwell equations for the electromagnetic field united all that was up till now known concerning electricity and magnetism and predicted the existence of the electromagnetic phenomenon which can travel as waves having the velocity of 1/√ε0μ0 in a vacuum. The velocity that is based on constants obtained from purely electric measurements corresponds to the speed of light. As a result, Maxwell concluded that light itself was an electromagnetic phenomenon. Afterward, Einstein's special relativity theory hypothesized that the value of the speed of light is independent of the motion of the source of the light. Since then, the speed of light has been computed having increasing accuracy. In the year 1983 it was stated to be exactly 299,792,458 meters per second. Altogether having the cesium clock, which consists of been employed to state the second, the speed of light serves up as the latest standard for length.

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