Shocking Science of Electric Eels

Following on from my discussion on BBC Radio Cambridgeshire about the scientist electrocuting himself with electric eels I got to interview the man himself for the Naked Scientists…

In the 1800s, whilst exploring the Amazon, naturalist Alexander von Humboldt documented an attack on a horse by an electric eel, which allegedly leapt out of the water to stun the animal… Yet despite being studied for over 200 years since, this – and the video on YouTube below – were the only documented claims of this behaviour, until, that is, Vanderbilt University’s Ken Catania got his hands on an electric eel. Literally…

  • Electric eels use their shock to freeze-up animals for predation
  • Ken discovered the leaping behaviour when an eel jumped out of the water to attack the net that he was holding
  • He wanted to measure all of the variables in the electric circuit formed by the eel and its prey
  • To do this he used himself as bait and allowed the eel to shock his arm so that he could measure the current and resistance
  • The small eel he was working with gave off 200 volts but larger ones could reach up to 500 – the equivalent of 20 tasers
  • The current of 40-50 milliamps flowing through his arm was sufficiently painful to cause an involuntary reflex action to remove his arm

You can listen to the full interview here.

 

 

 

Pokémaths: how many Pikachus does it take to power a light bulb?

The mascot of the Pokémon world and probably the most famous of all the Pokémon: Pikachu. It’s pretty much just a short, chubby rodent with two red circles on its cheeks that it apparently uses to store electricity. So the obvious question to ask here then is how many Pikachus would it take to power a lightbulb?

The official Pokédex tells us that Pikachu is able to ‘release electric discharges of varying intensity’ and is also known to ‘build up energy in its glands that needs to be discharged to avoid complications’. Quite what these ‘complications’ might be I’m not sure – suggestions on a postcard. The Pokédex also says that the tail of a Pikachu plays an important role as it acts as a grounding rod to prevent the creature from electrifying itself and also allows one Pikachu to recharge another one that’s running low on juice. Another fun fact about Pikachu’s tail is that a female will have a v-shaped notch at the end which is not present on males. Next time you’re out Pikachu hunting, now you know.

When a Pikachu uses its signature move, thunderbolt, it releases 100,000 volts of electricity. You might think that this would be enough to kill you, never mind just power a lightbulb and you wouldn’t be wrong, but there’s a little more to it than that. When someone dies from electrocution, it isn’t the voltage that kills them, it’s the current. If a current of just 7 milliamps reaches your heart for around 3 seconds its lights out. The current is tiny, but it disrupts the hearts natural rhythm causing it to stop. You can of course be electrocuted and live to tell the tale, but this means that you were very lucky in that the path that the electricity chose to take through your body must have avoided your heart. In general, electricity will flow along the path of least resistance, as with most things in nature it’s lazy and so takes the path that is the easiest.

I’ve now mentioned three terms, which means a good old fashioned physics formula triangle. The particular one we want here is Ohm’s Law:

triangle2

The resistance of your body is around 100,000 ohms, which means thunderbolt generates a current of 1 amp that will flow through your body. In other words, if it hits your heart you’re toast.

Now onto lightbulbs. They come in all sorts of different shapes and sizes, and different amounts of wattage or power. The standard one is 60 watts and that’s the one we’re considering here. None of these fancy energy saving bulbs that start off really dim so that you can’t see a thing and gradually build up in brightness… (don’t get me started on them). The key bit of physics that we need relates power (in watts) to Ohm’s Law above and states:

trinagle1

For a 60 watt light bulb attached to the UK mains supply of 230 volts, this generates a current of 0.26 amps. If we were to connect the bulb up to a Pikachu using thunderbolt the current decreases hugely to only 0.0006 amps. The light bulb will still work but the current will just be very small. This means only a small wire is required and also has the added benefit of reducing the chance of electrocution… However, 0.0006 amps is still enough to kill you if it hits your heart, so be careful next time when you’re hooking up your lightbulb to a Pikachu!

 

All of the material in the Pokemaths series can be found here.

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