Last Friday Tom Vales came to our class and did a presentation on electricity. It was really very interesting. He first showed us several small energy conversion devices.

The first device was a thermoelectric device made of copper wire and bismuth. It ran by having one wire in hot water and the other in cold water.

The next and my favorite, was the Stirling engine which was invented in 1816 by Richard Stirling. It is a heat engine and Vales small version was running off warm water in a cup. Mr. Vales said that it was so sensitive that the water barely has to be warmer than the surrounding temperature( about a 4 degree Celsius differential). He said that it had been invented to replace the steam engine but this didn’t really work out because on a larger scale the engine can be dangerous because of …well its tendency to explode. I like this technology anyway because it is 80% or more efficient. It is employed submarines because it is very quiet and small generators run by propane. The technology hasn’t changed since it was invented.

Mr. Vales Stirling engine looked like this.

 

Hey cool, a fancy Steampunk version

This is a schematic of how a Stirling engine works.

It runs off hot and cold currents alone(moving hot air back and forth),  how cool(and warm) is that?

Next he showed us a simple Barbeque lighter. He said that a quartz crystal and mechanical stress are enough to generate a high voltage. He called this the Piezoelectric effect.This is a charge that naturally accumulates in certain solid materials.

After this he showed the Mendocino motor. He said it was made up of magnets, balsa wood, and four solar cells tied to a winding. A current is put through the winding which reacts with the magnetic fields.

Mr. Vales said that the device can reach 1,500 RPM in full sun but is very fragile because the touching it while running would disrupt the delicate balance between gravity and the magnetic fields and it is more of a teaching tool than anything else.

Vales spent the rest of the presentation talking about Nikola Tesla and showing us his home-made Tesla coil which was a bunch of copper wire wrapped around an upside down plastic bucket. He told us that Tesla’s dream was the wireless transmission of energy and that this dream may have been achievable back in his time but not in ours. Vales made us all very nervous by holding a variety of bulbs up to his Tesla coil, on the top of which was a spark, and causing them to light up with energy. He said that he was safe from being electrocuted and that he only felt his arm getting warm,  but the electricity being generated was still dangerous. He said that he was experiencing the skin effect, which means the current travels over the outside of the conductor not through it.   It was impressive when the xenon filled bulb he held up lit up “remotely”. He also put a piece of  magnet wire (copper wire covered in lacquer) on top of the coil and the current running through it made it spin around.

I think one of the neatest things I learned about was St. Elmo’s fire. St. Elmo’s fire is stated in Wikipedia as “a weather phenomenon in which luminous plasma is created by a coronal discharge from a grounded object in an electric field in the atmosphere (such as those generated by thunderstorms created by a volcanic eruption)” . Mr. Vales said it shows up on the masts of ships or wings of planes and shows up as a purple flame.

I would like to thank Mr. Vale for finding the time to come show our class some very interesting  energy conversion devices and for risking getting himself electrocuted to show us some very neat tricks with electricity.