In this YouTube video, a fellow runs 10 amps through a cylinder of pencil graphite, burning his fingers (accidentally on purpose, I'd say).
He has a good article about graphite on his site:
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Graphite is highly conductive unlike diamond or wood. But it is conductive along the layers, not perpendicular to them. It has many different applications. Generally it is crushed into powder that can be used to make other components like battery rods, deposited traces on electronics and such.
But pencils are the most basic use of them. If you draw a thick line using pencil on paper and measure the resistance across it, you will see your line is conductive, and if you bring your probes closer on the paper over the line, the resistance gets lower, like a potentiometer.
Protip: when powerlines fall on your chainlink fence, remove yourself from proximity to the chainlink fence. Read the rest
When we think about threats to America's energy infrastructure, we usually think about hackers. Hackers, or maybe, somebody taking a bomb to a nuclear power plant.
What we don't usually think about is some guys with guns.
According to a Wall Street Journal report by Rebecca Smith, last April a group of snipers cut the phone lines and internet access near a major electrical substation in San Jose, California, and then fired on the substation for 19 minutes, knocking out 17 transformers. Read the rest
A case study in the New England Journal of Medicine details the tragic story of an electrician who received a shock of 14,000V and was blinded as part of his injuries. Accompanying the article is this striking photo of the scars on his eyes, which resemble the plasma ball effects, the sort of thing you'd expect from a science fiction movie. Read the rest
On the East Coast of the US, electric demand is so high that utility companies can't take major transmission lines out of commission for maintenance and repair. Instead, workers fly up to the affected cable in a helicopter and work on the line while it's live — coursing with electricity. The helicopter hovers next to the line and the lineman leans out of a little bucket on the side and does his or her job, protected from electrocution by the same loophole that allows birds to safely land on those lines. As long as the entire contraption — lineman and helicopter — don't create a pathway from an area of high energy (the powerline) to an area of lower energy (the ground, for instance, or another power line that operates at a lower voltage) they're good to go. In order to do that, they have to energize the helicopter to the same voltage as the line.
Also check out this longer video with GoPro-style footage of helicopter-assisted transmission line repair and a British documentary following some of the men who do this job. Around six minutes in, the documentary has a nice explanation of how the workers energize the helicopter without killing themselves. Also, according to one of the linemen, "chicks dig it". Read the rest
If you enjoy the irony in the fact that the great East Coast blackout of 2003 was largely caused by a few untrimmed trees, then you're going to love Jon Mooallem's account of how America's squirrels are wreaking havoc on America's electricity system.
Using a Google news alert, he's cataloged 50 squirrel-caused power outages in 24 states — and that's just since Memorial Day. These aren't small outages either. Several of them have cut power to thousands of people at a time. Back in 1994, a squirrel took out the Nasdaq. These are kamikaze raids and they've led to an interesting phenomenon — technology developed specifically to protect our infrastructure from furry, tree-hopping rodents.Read the rest
"A concert on the engineering quad, University of Illinois," explains Tau Zero. "The arcs reproduced the fundamental tones of music played back through a PA system. Part of the Engineering Open House." Read the rest
The Joule Thief is a way of producing enough electricity to run small, but useful, electric lights using cast-off trash like pop-can tabs and "dead" batteries. It's especially handy in the Himalayas, writes inventor and Google Science Fair judge T.H. Culhane. There, electricity is a precious resource. But the components needed to build a Joule Thief are abundant, thanks to climbers and tourists who leave behind all sorts of surprisingly useful litter.
Last week, Culhane joined a G+ hangout sponsored by National Geographic and Girlstart to talk about the value in things we throw away and walk viewers through the construction of their very own Joule Thief. You can watched the video of the event, or read the instructions for building a Joule Thief at Culhane's blog.
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The fact that the Joule thief allows one to run a 3V LED from a 1.5 or 1.2 Volt battery would itself be astounding, because it means you only need half the number of batteries to get the same light.
Some of you are thinking "wait, maybe it enables you to use a single 1.5 volt battery to light a 3V LED instead of the usual two, but doesn't it just make that battery last half as long? Great question, but the answer is that the Joule Thief, which works by building up and collapsing a magnetic field around the torus (which acts as an electromagnetic inductor) actually is more efficient than using a battery directly because it PULSES the energy to the LED.
Salt water is still winning. Unfortunately.
Remember back during the Fukushima crisis, when you heard a lot of talk about why the people trying to save the plant didn't want to use sea water to cool the reactors? There were a number of reasons for that (check out this interview Scientific American's Larry Greeenemeier did with a nuclear engineer), but one factor was the fact that salt water corrodes the heck out of metal. Pump it into a metal reactor unit and that unit won't be usable again.
Now, the corrosive power of salt water is in the news again — and this time it's ripping through New York City's underground network of subways and utility infrastructure. I like the short piece that Gizmodo's Patrick DiJusto put together, explaining why salt water in your subway is even worse than plain, old regular water:
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When two different types of metal (or metal with two different components) are placed in water, they become a battery: the metal that is more reactive corrodes first, losing electrons and forming positive ions, which then go into water, while the less reactive metal becomes a cathode, absorbing those ions. This process happens much more vigorously when the water is electrically conductive, and salt water contains enough sodium and chloride ions to be 40 times more conductive than fresh water. (The chloride ion also easily penetrates the surface films of most metals, speeding corrosion even further.) Other dissolved metals in sea water, like magnesium or potassium, can cause spots of concentrated local corrosion.