Advice 1: What is ampere

The unit "ampere" is used to measure the strength of an electric current all over the world. But few people think about for what reason this unit got its name.
The name of the unit of current "ampere" received from the surname of the French physicist Henri-Marie (in another transcription - andré-Marie) Ampsand who lived in the period from 1775 to 1836. The main sphere of his activity was the study of electromagnetic phenomena, while he established, in particular, that the strength of the magnetic field generated by the conductor with current depends on the strength of this current, not voltage. For this reason, it is named after the unit of current strength, and not any other electrical values.Other areas of physics Henri Amps little interest. Nevertheless, it was he who coined the term "Cybernetics, not Norbert Wiener, who only gave him a new value. The term "kinematics" refers to the field of physics, which in all secondary schools studied even earlier electromagnetic phenomena, Ampere also invented. He also studied botany and even philosophy.If placed in parallel in a vacuum two infinitely thin wire, place them at a distance of exactly one meter from each other and pass through each of them a current of one ampere, they will interact with the power of two by ten to the minus seventh Newtons. Thus, through each one of them will be 6,2415093 ten to the eighteenth degree of electrons per second.Amper linked to other units of measure: volt, Ohm and watt. If the conductor resistance of one Ohm voltage is applied in one volt through it flows a current of one ampere. In this case, it will stand out in the heat one watt of power.If to measure length and weight in different countries use different units, the volts, amperes, ohms and watts adopted as official units, respectively, voltage, current, resistance and power in all countries without exception.

Advice 2: What are stray currents

Stray currents – electrical currents in the ground that appear when you use it as a conducting medium. Under their action occurs the corrosion of metallic objects in the ground or come in contact with it. As a rule, these objects are a shell of electric cables, various building structures and pipelines.
Stray currents typical for electrified railway and tram tracks, which are serviced improperly or accidental leakage from power lines. Sometimes such currents is called zero current, which exist in the grounded metal structures.

Sources of stray currents.

Sources of currents in the earth are underground, tram, electrified with direct current suburban rail transport. The wires in these types of transport are connected with a plus power source and a minus, with a return conductor rail tracks.
Products humus, alkali, lime, sour marshy soils containing lime, slag, ash creates conditions for intensive soil corrosion of the shells of metal.

Because of poor isolation of the roadway from the ground, a large resistance of track, as well as violations of the joints of the rail, part of the current passes to the negative pole of the power source via earth. Meeting on the way the metal sheath of cables, pipelines and other underground structures, currents pass through these conduits and returning to the earth to get to minus traction substation.

Throughout this chain the path of the electric current there is a phenomenon of electrolysis. Where the metallic sheath of the cables and track are the electrodes (anode and cathode) and the damp soil containing large amounts of salts and acid – electrolytic environment (electrolyte). And if you move to DC current through the electrolyte, the electrode with higher potential dissolves.
Electrolysis – the process of separating components of substances in solution, by passing electric current through it.

Scientists have calculated that the magnitude of stray current in one ampere, in one year destroyed 33 pounds of lead, 3.95 kg aluminum and 9 pounds of iron. The strongest destruction of exposed lead sheath on the cable lines.

Prevention of stray currents

To protect underground structures and metal sheaths of cables from corrosion stray currents take special measures:
- as far as possible to reduce the resistance of the rail by welding of joints of rail and isolate the rail from the ground.
- to reduce the voltage drop in the rails using special line of the cable connecting different points of the rail with the negative bus of the substation.

These methods achieve significant unloading rail network and reduce the number of stray currents.
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