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Monday, 9 February 2015

An Electrode

electrode


An electrode is an electron conductor together with a counter electrode with a medium located between two electrodes interacts. Electrodes are serene of electrical conductors, frequently a metal or graphite. They are used to connect non-electron-conducting regions with cables and find this example application in electrochemical cells, as a tool (eg. As in resistance spot welding) and possibly material dispenser during arc welding, as terminals and electro-optical elements in electron tubes. About the electrical function beyond electrode material may be deposited or consumed, or there may be physical processes taking place in the electrode as the anode of an X-ray tube.

 Electrodes in the gas or vacuum or insulator
 Depending on the type of the medium surrounding the electrode leads to different forms of interaction:

 If the medium is an insulator, an electric field is established between the electrodes. This pattern is called condenser. however, silent electric discharge.

 If the medium is a vacuum or a gas, so an electric field between the electrodes is built up as in the case of the insulator. However, electrons from one electrode (cathode) move to another when the exit from the cathode is made possible, eg. As by field emission or thermal emission or the Thermionic emission (→ electron tube, x-ray tube, thermionic cathode).

 If the medium is a gas, the atoms or molecules of the gas are partially ionized, so that a plasma is formed. In plasma, the ions move next to the electrons in the electric field (→ gas discharge lamp).


 Also, the spark plug electrodes, welding electrodes in arc welding and the electrodes inside the nozzle for plasma cutting fall into this category. The welding electrodes generate an arc welding with the material to be welded. In the heat of the arc both melt and the electrode is used as filler material, so that the materials are joined.

Transformers

transformr

Electromagnetic transformers are static devices that starting from an alternating voltage connected to its input, other than the previous gain in the transformer output voltage varying alternating. And allow to provide an adequate tension to the receiver characteristics. They are also essential for transporting electricity over long distances at high voltages, with minimal losses and moderate conductive sections.

Consist essentially of a closed magnetic circuit on which two windings, so that both windings are crossed by the same magnetic flux are wound. The magnetic circuit is constituted (for industrial frequency of 50 Hz) of steel sheets stacked little thickness, to prevent eddy currents.

Winding where the input current is connected is called the primary, and the winding where the payload is connected, is called secondary. The alternating current flowing through the primary winding magnetizing the core alternately. And the secondary winding is traversed by a variable magnetic flux in an approximately sinusoidal flux variation and this engenders by Lenz's law, an alternating voltage in said winding.

FUNDAMENTAL EQUATIONS

The effective value of the electromotive force in the windings of the transformer is determined by the following formulas:



U1 = 4.44 BM A f n1

U2 = 4.44 BM A f n2

Where:

U1 = voltage at the primary winding (volts)

U2 = voltage in the secondary winding (volts)

BM = maximum value of the flux density in the core (Tesla). (In magnetic iron core transformer usually has a maximum value of 1.4 Tesla)

f = frequency of the alternating current (Hz)

n1 = number of turns of the primary winding (dimensionless)

n2 = number of turns of the secondary winding (dimensionless)

A = cross sectional area of the magnetic core (m2)



If the primary and secondary are traversed by the same maximal induction BM & A section of the core remains constant, then;

U1 / U2 = n1 / n2

This ratio is called transformation ratio, and indicates the relationship between input and output voltage, when the transformer is idling, or unloaded, in the secondary.