Electricity

[restrict]Training Program:  Basics of Electricity

A LITTLE HISTORY:  The history of electricity begins with William Gilbert, a physician who served Queen Elizabeth I of England. Before Gilbert, all that was known of electro-magnetism was that lodestones possessed magnetic properties; and that rubbing amber and jet would attract bits of stuff to start sticking. In 1600, William Gilbert published his treatise De magnete, Magneticisique Corporibus (On the Magnet). Printed in scholarly Latin, the book explained years of research and experiments on electricity and magnetism. Gilbert raised the interest in this new science greatly.

Inspired and educated by William Gilbert several Europeans inventors, Otto von Guericke of Germany, Charles Francois Du Fay of France, and Stephen Gray of England, expanded the knowledge. Otto von Guericke proved that a vacuum could exist. Creating a vacuum was essential for all kinds of further research into electronics. In 1660, Otto von Guericke invented a machine that produced static electricity: this was the first electric generator. In 1729, Stephen Gray discovered the principle of the conduction of electricity. In 1733, Charles Francois du Fay discovered that electricity comes in two forms which he called resinous (-) and vitreous (+), now called negative and positive.

An early battery, or capacitor (a device that stores and releases an electrical charge), was the Leyden Jar which was invented in 1745 by men in Holland and Germany nearly simultaneously. Until that time electricity was considered a rather mysterious fluid or force. In 1752 Ben Franklin flew a kite with his son, learning that electricity and lightning were one and the same. Franklin’s lightning rod was the first practical application of electricity.

Since then many, many scientists have added to our current knowledge of electromagnetism. We now know that electricity is comprised of electrons (carrying a negative charge) & protons (carrying a positive charge). These protons are basically trapped inside their nucleus and can’t escape, so it is moving electrons that are primarily responsible for electricity!  Below are some of the terms used when discussing this electricity – which the human race seems to be so obsessed with creating, storing, and distributing to every individual.

AC or Alternating Current – electricity which reverses direction sinusoidally (in waves). In the US most household current is AC at 60 cycles per second.

Amperes – The SI unit used to measure electric current: a measure of the amount of electric charge flowing past a circuit point at a specific time One ampere is equal to a flow of one coulomb per second, or a flow of 6.28 × 1018 electrons per second.

Base-load – The more or less constant part of the total load on an electrical power-supply system.  The minimal current across an electrical grid below which power outages may result.

Battery – Invented by Volta in 1800, a battery is a storage device that converts chemical energy into electrical energy. They may be wet cells (a car battery) containing free liquid electrolytes or dry cells (cell or flashlight battery) where electrolytes are held in an absorbent material.

It should be noted that, generally, a battery can also be any object which contains potential energy stored for later production such as a dammed lake (with a generator in that dam) or a heated salt loop (at some solar power stations).

Capacity or Capacitance – Electrical phenomenon whereby an electric charge is collected or stored. Represented by the symbol C; capacitance is measured in farads.

Conductivity – 1) the property of transmitting heat, electricity, or sound.  2) a measure of the ability of a substance to conduct electricity. The SI unit is siemens per metre (S/m).

Converter – Any device for changing alternating current to direct current, or direct current to alternating current. Note: Nuclear converters also exist – a nuclear reactor that converts fertile atoms into fuel by neutron capture, using one kind of fuel and producing another.

Coulombs – Named for French physicist Charles Augustin de Coulomb (b. 1736), this is a SI derived unit of electrical charge equal to the amount of charge transferred by a current of 1 ampere in 1 second .

Current – A flowing movement in a liquid, gas, plasma, or other form of matter, especially one that follows a recognizable course. An Electric Current happens any time an object with a net electric charge is in motion, such as an electron in a wire or a positively charged ion jetting into the atmosphere (as in solar flares). Electrical signals transmitted through a wire generally propagate at nearly the speed of light, but the current in the wire actually moves very slowly: pushing electrons into one end of the wire is rather like pushing a marble into one end of a tube filled with marbles. A marble (or electron) gets pushed out the other end almost instantly, even though the marbles (or electrons) inside move only incrementally. Since electrons have a negative charge, current in an electrical circuit actually flows in the opposite direction of the movement of electrons!

DC or Direct Current – an electric current of constant direction, having a magnitude that varies slightly if at all.

Electrical Motor – Any machine which converts electrical energy into mechanical energy. In some instances electric motors can operate in a braking mode to produce electricity from mechanical energy. Small motors may be found in electric watches. The largest electric motors are used for ship propulsion, pipeline compression, etc.

Farads – named after Michael Faraday (b. 1791) these are represented by the symbol F. This SI term is capacitance that has an equal and opposite charge of 1 coulomb on each plate and a voltage difference of 1 volt between the plates.

Generator – machine used to change mechanical energy into electrical energy. It operates on the principle of electromagnetic induction discovered in 1831 by Michael Faraday. The mechanical power often comes from turbines powered by water, wind, steam, or gas.

Ground or Earth (symbol ⏚) – A reference point in an electrical circuit from which voltages are measured; or a common return path for electric current; or a direct physical connection to the Earth. The use of the term ground (or earth) is so common that circuits in portable electronic devices such as cell phones as well as circuits in vehicles may be spoken of as having a “ground” connection without any actual connection to the Earth.

Intermittent – ??

Kilo Watt-hour or kWh – unit of energy equal to the work done by 1000 watts operating for one hour.

Ohms – Named for Georg Simon Ohm (b. 1789); The SI derived unit showing electrical resistance. One ohm is equal to the resistance of a conductor through which a current of one ampere flows when a potential difference of one volt is applied to it.

Parallel Circuits – method for connecting an electrical circuit. Unlike a series circuit, components in parallel circuits are wired separately to the source; so all but one light could be burned out and the last one will still function.

Peak-load – the maximum load on an electrical power-supply system; above which wires could melt, short-circuit, or simply engage a circuit-breaker.

Polarity – Intrinsic polar separation or orientation. The manifestation of two opposite or contrasting tendencies, especially regarding the (+) or (-) of magnetic or electric poles.

Resistance – how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. Resistivity is commonly represented by the Greek letter ρ (rho). The SI unit of electrical resistivity is the ohm⋅metre (Ω⋅m).

Static – 1) Objects having no motion, or producing stationary charges.  2) Crackling in a receiver or specks on a television screen, produced by signal disturbance.

Système International d’Unités or SI – system of measurable units adopted by the 11th General Conference on Weights and Measures (1960). It is based on the metric system.

Series or Current-coupled Circuits – method for connecting an electrical circuit. As in a string of Christmas tree lights, every device must function for the circuit to be complete; one bulb burning out breaks the circuit.

Siemens – abbreviated S, it is named after EW von Siemens. A unit of electric conductance in the International System of Units (SI). Conductance is the reciprocals of resistance; hence one siemens is equal to the reciprocal of one ohm, and is also referred to as the mho.

Transformers – Device that transfers electric energy from one alternating-current circuit to one or more other circuits, either increasing (stepping up) or reducing (stepping down) the voltage. Uses for transformers include reducing the line voltage to operate low-voltage devices (doorbells or toy electric trains) and raising the voltage from electric generators so that electric power can be transmitted over long distances. Transformers act through electromagnetic induction (i.e. current in the primary coil induces current in the secondary coil).

Volts – Named after Italian scientist Alessandro Volta (b. 1745), it is abbreviated V. An SI unit describing the difference of electric potential existing across the ends of a conductor carrying a constant current of 1 ampere when the power dissipated is 1 watt. US power lines are often 120 volts of alternating current. For direct current it is a measure of power and is the same as a watt; for alternating current it is a measure of apparent power.

Watts – an SI unit of power equal to 1 joule per second; the power dissipated by a current of 1 ampere flowing across a resistance of 1 ohm. Named after Scottish engineer James Watt(b. 1736), 746 watts equals one horsepower.

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