Mystery of "V x I" and AC (Alternating Current)

Mystery of "Power = V x I" and AC (Alternating Current)

V (Joule/Coulomb) x I (Coulomb/second) = Power (Joule/sec = Energy/sec). So after multiplication of V by I, Coulomb (unit of electric charge) disappears like a magic and only Energy and time remain. This explains well that Current is not consumed in a load such as a resistor and a light bulb - Kirchhoff's Current law but Energy is consumed, changed to some other form of Energy - conservation of Energy.

Another mystery - AC (Alternating Current)

Some people may think that Current flows very fast in a conductor like a light or electromagnetic wave because of the flow of electrons and moves back and forth in case of AC also very fast (between a Power station and home), which is totally wrong. The following article is very good for common ordinary people.

Issued by U.S. Department of Labor IV. PROPAGATION OF ELECTROMAGNETIC ENERGY:


Most people, including most electrical engineers, think of electricity as electrons flowing in a wire, much like water flowing in a hose. The idea of electrical energy moving through free space in a wave is a completely foreign concept. Yet, electromagnetic radiation is exactly that, electrical energy moving through space as a wave, and electrical energy in a wire is a special case in which the energy is guided by a wire. Some of the energy is internal to the wire, and some of the energy is external to the wire. When we plug an appliance into the receptacle, the power delivered to the appliance does not actually "go through the cord", but is electromagnetic energy being "guided" by the electron activity in the power cord. The electromagnetic energy delivered to the load is external to the wire. The electron activity oscillating back and forth in the wire is a result of the external electromagnetic energy and in turn serves as a way of telling the electromagnetic wave to follow the wire. The electron movement in the wire is proportional to the strength of the wave being guided. Don't be disturbed if you have difficulty grasping this concept. Even engineering students have difficulty understanding it.


Ref

http://www.osha.gov/SLTC/radiofrequencyradiation/electromagnetic_fieldmemo/electromagnetic.html

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