## Monday, 8 December 2008

### Let It Flow

I worked as an electrician for 15 years. I now realise just how little I know about what electricity actually is. All I knew was that it hurt when I touched live cables (which was likely to make me scream); I also realised it was dangerous when it blew holes in my pliers because I'd cut through a live cable (which also made me scream). Other than that, I'd always suspected it was a substance that flowed from a power station, across fields and along cables until it reached a socket in the lounge. As it happens, this is not quite the case.

An element's emission spectrum is the relative intensity of electromagnetic radiation of each frequency it emits when it is heated, or more generally when it is excited. Electromagnetic (EM)radiation takes the form of self-propagating waves in a vacuum or in matter. EM radiation carries energy and momentum, which may be imparted when it inter-acts with matter. An important aspect of the nature of light is frequency. The frequency of a wave is its rate of oscillation, and is measured in hertz. One hertz is equal to one oscillation per second.

At the end of the 19th century, physicists knew there were electrons inside atoms, and that the wiggling of these electrons gave off light, and other EM radiation. EM waves were first postulated by James Clerk Maxwell, and subsequently conirmed by Heinrich Hertz. Maxwell concluded that light itself is an EM wave. According to Maxwell's equations, a time-varying electric field generates a magnetic field - and vice versa. Therefore as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These osillating fields together form an EM wave. Radiation is caused by wiggling charges, and the rate of the wiggling determines the wavelength.

Electric power is defined as 'flow of energy'. Electric current is a flow of electrons - but the electrons don't flow forward, instead they vibrate slightly. The frequency of this vibration is slow (standards are around 50-60 Hz) when compared to other forms of EM radiation. I am now starting to think of electricity as a radiowave. Tesla's ultimate application of free energy was as a radiowave. I found this offering on YouTube, which is an example of wireless electricity: