Secondat: Tesla

Sunday, April 19, 2009

Tesla

A little over a year ago, Wired mag showed this photo of fluorescent light bulbs being wirelessly powered by overhead powerlines.

{source: wired.com}

There are more photos here and here.

The man who devised this display, Richard Box, is a British artist. His web site quotes an article in the Guardian:

The 1301 fluorescent tubes are powered only by the electric fields generated by overhead powerlines.

Richard Box, artist-in-residence at Bristol University's physics department, got the idea for the installation after a chance conversation with a friend. 'He was telling me he used to play with a fluorescent tube under the pylons by his house,' says Box. 'He said it lit up like a light sabre.'

Box decided to see if he could fill a field with tubes lit by powerlines. After a few weeks hunting for a site, he found a field, slipped the local farmer £200 and planted 3,600 square metres with tubes collected from hospitals.

A fluorescent tube glows when an electrical voltage is set up across it. The electric field set up inside the tube excites atoms of mercury gas, making them emit ultraviolet light. This invisible light strikes the phosphor coating on the glass tube, making it glow. Because powerlines are typically 400,000 volts, and Earth is at an electrical potential voltage of zero volts, pylons create electric fields between the cables they carry and the ground.

Box denies that he aimed to draw attention to the potential dangers of powerlines, 'For me, it was just the amazement of taking something that's invisible and making it visible,' he says. 'When it worked, I thought: 'This is amazing.'

The electric field generated by the powerlines is called powerline radiation or EMF powerline radiation (EMF: electric and magnetic field). The US Environmental Protection Agency has put out an info leaflet on its possible harmful effects: Electric and Magnetic Field (EMF) Radiation from Power Lines (pdf). An internet search of the term will bring up many other sources.

Nikola Tesla was the first to notice the phenomenon. The wikipedia article on Tesla describes his precursor of Box's glowing tubes:

Within a room were suspended two hard-rubber plates covered with tin foil. These were about fifteen feet apart, and served as terminals of the wires leading from the transformers. When the current was turned on, vacuum bulbs or tubes, which had no wires connected to them, but lay on a table between the suspended plates, or which might be held in the hand in almost any part of the room, were made luminous.

Here is a contemporary photo of the phenomenon:

{caption: an experiment in Colorado Springs; the bank of lights is receiving power from a distant transmitter; source: wikipedia}

Last Monday we visited the Smithsonian Museum of American History which has a section devoted to the origin of electrical power which now* gives some information on Tesla and his work. The man led a fascinating life, tormented by illness, subject to hallucinations, suffering from an obsessive/compulsive disorder, he was a combative genius. Many of his 700 patents would qualify him as one of the 20th centuries greatest inventors, but probably the greatest is the alternating current induction motor: the common electric motor which caused a revolution in manufacturing, commerce, transportation, and the conduct of most people's daily existence.

Some Tesla links (many of them from the wikipedia article):