Induction, electromagnetic

The concept of a vector flux d through a surface dS has been given in Sections (2.8.3) and (4.1.3). Being a particular case of a more general theory of a vector field, the same concepts can be applied to a magnetic field as well. An elementary flux d of a magnetic field induction vector B through the surface dS is equal to a scalar product of B and dS 

In 1812 the English physicist Michael Faraday made a discovery, which has significantly influenced the development of all mankind. Having made a real conducting contour, confined to a surface S, he established that by changing the flux (5.1.34) an electric current appeared in the circuit. By numerous experiments, Faraday established that current value does not depend on the way the flux changes but on the speed of this change. The mathematical form of Faraday s law is extraordinary simple  

The minus sign in this expression corresponds to the general physical law of inertia the induction current in a contour is always directed in a way that opposes the reason of its appearance. This statement is referred to as the Lenz rule. 

This field is not electrostatic because it has been created in a different way - the movement of charges in a magnetic field. The circulation of the electric field strength E along the contour will produce EMF in the contour (see eq. (5.1.8))  

Only the movable part of the contour creates EMF, therefore 

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Isaac Newton modestly claimed to have stood on the shoulders of giants to explain how he was able to achieve his outstanding discoveries in the fields of gravitational attraction and planetary motion our Giants in the field of electromagnetic induction would probably have said the same. 

Exciting developments based on electromagnetic induction raced along from that time, giving us the sophisticated products our everyday lives depend on. During most of the period productive uses for eddy current technology were few and few people believed in it as a usefiil tool eddy currents caused power loss in electrical circuits and, due to the skin effect, currents flowed only in the outer surfaces of conductors when the user had paid for all the copper in the cable. The speedometer and the familiar household power meter are examples of everyday uses that we may tend to forget about. The brakes on some models of exercise bicycle are based on the same principle. 

Faraday is better known in chemistry for his laws of electrolysis and in physics for proposing the relationship between electric and mag netic fields and for demon stratmg the principle of electromagnetic induction... 

Induction furnaces utilize the phenomena of electromagnetic induction to produce an electric current in the load or workpiece. This current is a result of a varying magnetic field created by an alternating current in a cod that typically surrounds the workpiece. Power to heat the load results from the passage of the electric current through the resistance of the load. Physical contact between the electric system and the material to be heated is not essential and is usually avoided. Nonconducting materials cannot be heated directiy by induction fields. 

Pitch-based fibers generally have higher moduh but lower strengths than theh PAN-based counterparts. The specific properties of the various types of carbon fibers are compared in Figure 4. Pitch-based fibers also have higher electrical conductivity, which can be an important consideration in certain circumstances, for example, for use in electromagnetic inductance (EMI) shielding. 

A transformer has both dielectric capacitances and electromagnetic inductances. Surge transference thus depends on the electrostatic and electromagnetic transient behaviour of these parameters as noted below. 

Transposing the overhead communication lines, i.c. reversing the respective positions of the two sides of the lines every I km or so, to avoid continuous parallelism (due to electrostatic and electromagnetic inductions), as illustrated in Figure 23,8.. See also Section 28.8.4(3) on phase transposition. 

All ctfecis caused by electrostatic or electromagnetic inductions are termed Inductive Interferences. With the use t)f glass optical fibre cables in new installaiioiis. this effect is overcome automatically. Optical fibre cables, as discussed later, have no metal content and cany no electrical signals. Therefore the above discussion is more appropriate for existing installations and also to provide a theoretical aspect and moi c clarity on the phenomena of inductive interferences. These can also be applied to other fields rather than communications alone. 

The electrical age was built on the discovery in the early 1830s, independently by Joseph Henry (1797-1878) in America and Michael Faraday (1791-1867) in England, of electromagnetic induction, which led directly to the invention of the dynamo to generate electricity from steam-powered rotation. It came to fruition on New Year s Eve, 1879, when Thomas Edison (1847-1931) in rural New Jersey, after systematic and exhaustive experiments, made the first successful incandescent lamp, employing a carbonised filament made from some thread taken from Mrs. Edison s sewing cabinet. The lamp burned undimmed for 40 h, watched anxiously by Edison and some of his numerous collaborators. This lamp was ideal for... 

Strom-geschwindigkeit, /. velocity of current, -indikator, m. current indicator, -induktion, /. induction of cmrents. electromagnetic induction. -kreia, m. (Elec.) circuit, -kreis-unterbrecher, m. circuit breaker, -lauf, m. flow d current, -leistung, /. (Elec.) power, wattage, -leiter, m. ( Jiec.) conductor, -lei-tung,/. (Elec.) conduction. -Hnie,/. streamline. 

Alternating-current motors are classified as induction motors or synchronous motors. Faraday found that a stationaiy wire in a magnetic field produced no current. However, when the wire continues to move across magnetic lines of force, it produces a continual current. When the motion stops, so does the current. Thus Faraday proved that electric current is only produced from relative motion between the wire and magnetic field. It is called an induced current—an electromagnetic induction effect. 

In 1878 Hertz enrolled at the University of Berlin to study under Hermann von Helmholtz, the leading German physicist of the time. He obtained his degree magna cum laude in 1880 with a theoretical dissertation on the electromagnetic induction of currents in... 

Transformers were developed through a series of scientific discoveries in the nineteenth century. Most notably, Michael Faraday showed in 1831 that a variable magnetic field could be used to create a current, thus pioneering the concept of electromagnetic induction. It was not until the 1880s that Nikola Tesla was able to use this principle to bolster his patents for a universal ac distribution network. 

American physicist Joseph Henry discovers the principle of electromagnetic induction. English chemist and physicist Michael Faraday independently discovered the same principle a year later hut is the first to publish his findings. 

English chemist and physicist Michael Faraday discovers electromagnetic induction. 

During the next decades after the appearance of the Volta pile and of different other versions of batteries, fundamental laws of electrodynamics and electromagnetism were formulated based on experiments carried out with electric current supplied by batteries Ampere s law of interaction between electrical currents (1820), Ohm s law of proportionality between current and voltage (1827), the laws of electromagnetic induction (Faraday, 1831), Joule s law of the thermal effect of electric current, and many others. 

M. Klein J. Bolognese, "Investigation of the Feasibility of an Electromagnetic Induction Fuze for Photoflash Cartridges , PATR 1917 (Jan 1953)... 

English physicist who discovered electromagnetic induction and many other vital electrical and magnetic phenomena. 

Inductively coupled plasma (ICP) mass spectrometers use a hot plasma to ionize the sample. The plasma is generated by electromagnetic induction. The plasma source operates at... 

O. D. Jefimenko, Causality Electromagnetic Induction and Gravitation, Electret Scientific Company, Star City, WV, 1992. 

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