Physics

# An Overview of how Electricity Works

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Electricity is a virtual necessity in the modern world.  It is a part of most people’s lives even more than they realize.  Many people do not fully understand how this modern marvel powers all the things they do.

There are two basics forms of electricity, AC and DC.  AC stands for alternating current, and DC stands for direct current.  Both forms involve the flow of electrons to provide power to electrical circuitry, but the method of deliver is vastly different between the two.  When electrical distribution was first being considered, there was a battle between Edison, the proponent for DC, and Tesla, the proponent for AC, as to which would be used.  Tesla won, for many good reasons, and the 50 to 60 Hz AC system is what most of the world uses today.

AC is produced at a power plant by rotating a conductor in a magnetic field.  The produced voltage is at its peak when the conductor is moving perpendicular to the magnetic field, and it drops to a voltage of zero when the conductor moves parallel to the magnetic field.  Then the voltage changes polarity after passing through this zero voltage point and the cycle repeats.  For American power generators, this occurs 60 times per second to produce the 60 Hz AC that is required by electric products.  If you looked at the output of one of these generators, you would see a sine wave that produced a complete cycle 60 times a second.

The voltage that is produced in the American system has a peak of approximately 155 V, and a minimum of negative 155 V.  When discussing the voltage rating of a system the RMS, or root mean squared, voltage is commonly used.  This allows you to easily calculate the power that a device is using and provides a more useful “average” of the voltage that is provided, which is why the voltage produced in a standard American outlet is 110 V.

Much of Europe uses a 50 Hz AC system, and other countries use different frequencies and sometimes different voltages than the standard 110 V.  This is why a device that works in one country will not necessarily work with the power distribution system in another country.

DC is produced in a different manner.  It is a constant voltage, so the simplest method for producing it is in a battery.  Inside a battery, a chemical reaction occurs that causes electrons to be released, and these electrons flow through an attached circuit providing power.  The amount of reactants available decreases as the battery is used, which is why the voltage of a battery lowers over time until it is no longer capable of supplying the energy required by the device it is powering.  Rechargeable batteries utilize a reversible reaction, and so charging a rechargeable battery reverses the process, bringing the battery back to a like-new state for subsequent use.

A conversion can also be performed between the two types of voltages.  AC is converted to DC by first rectifying the output so that only positive voltage is produced, and then filtering this output until a steady DC output results.  Converting DC to AC is accomplished in a power inverter.  This process is more complicated and it is utilized much less frequently.

Electricity comes in two very different flavors, AC and DC, whose only commonality is that they both supply electrons to the powered device.  It is amazing to think of all the things that have to occur so that you can plug something in, push a button and have something happen.

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ARTICLE SOURCES AND CITATIONS
• http://www.kpsec.freeuk.com/acdc.htm