FEATURE

Power: from Atom to Application: A Six Segment FEATURE

The Science of Electricity         Power Generation        The Transformer        Interconnections         The Flow of Power         The Motion of Electricity        
PLUS
Seven Bullets: The Vulnerability of the Grid         The State of the Electric Grid        

The Motion of Electricity

Motion of electricity header



from - electriciantraining.tpub.com
Motion of electricity infographic Power = power is energy flow. Power is created by heat. Heat is created by joules which dissipate when an electric current of one ampere passes through a resistance of one ohm for one second. That is why electrical products (light bulbs, lap top computers) get hot. Power begins with the movement of electrons.

AC power doesn’t actually flow, nor does it travel inside a transmission line. AC power current likes to travel near the surface of a wire (skin effect). In DC power current travels through the whole of a wire. Due to the nature of an AC current, an electromagnetic field is created which surrounds and moves through the transmitting wire.

Electric charges typically flow as slowly as a river of warm putty. And in AC circuits, the moving charges don’t move forward at all, instead they sit in one place and vibrate. Energy can only flow rapidly in an electric circuit because metals are already filled with this “putty.” - from strategyand.pwc.com

In the case of a 12 gauge copper wire carrying 10 amperes of current (typical of home wiring), the individual electrons only move about 0.02 cm per sec or 1.2 inches per minute (in science this is called the drift velocity of the electrons.) The wire is “full” of atoms and free electrons and the electrons move among the atoms. In a typical copper wire there would be trillions of electrons flowing past any given point in the wire every second, but they would be passing that point very slowly. Think of the wire in comparison to a pipe full of marbles. If we push another marble into a filled pipe, then one marble would have to exit the other end. Electrons are like that in a wire. If one moves they all have to move.

The field associated with voltage is called the ELECTRIC (E) FIELD. It exerts a force on any electric charge placed in it. The field associated with current is called a MAGNETIC (H) FIELD, because it tends to exert a force on any magnetic pole placed in it. The below figure illustrates the way in which the E fields and H fields tend to orient themselves between conductors of a typical two-wire transmission line. The illustration shows a cross section of the transmission lines. The E field is represented by solid lines and the H field by dotted lines. The arrows indicate the direction of the lines of force. Both fields normally exist together and are spoken of collectively as the electromagnetic field.