Where Grey Matter meets Dark Matter

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Episode 19 - 18 October 2009

Magnetic induction makes the world go round! You want electricity? Well, most electricity generators use some form of induction. Even light waves or photons wouldn't work without it. "So what is it!?"

Well, it's good that you asked. Magnetic induction gets right to the heart of the meaning of 'electromagnetism'. On an earlier episode of the show (Episode 10), we talked about how an electromagnet is a lump of iron with a wire wrapped around the outside. When electricity is sent down this wire it magnetises the iron and you get an electromagnet, which can now pick up cars and dump them in the car-cuber. So electricity (which is just moving electrical charges, ie. electrons) makes a magnet. Now here's the kick in the pants: A moving magnet will make electricity in a nearby wire! Wham! The process is called 'induction'.

Source: All About Circuits

In this vid, the guy demonstrates different ways to get induction. The first thing he shows is what we're talking about here.
The others are just fancy ways to make magnets and then do the induction.

Induction is all contained in Maxwell's equations, which tell you everything you could possibly want to know about electricity, magnetism and light. So you can go and solve the equations, and you'll see that we're not lying (this time).

So power stations use exactly this idea of induction. A power station is essentially a device to spin a loop of wire near some magnets. It doesn't sound so bad, right? What could be bad about spinning wire? So then this whole thing about power stations being major world polluters is just media hype, right?! Wrong. It's how the power station gets the energy to spin this wire that is the problem. In a standard power station, you burn coal or gas, or split atoms, to generate heat. This heat boils water and makes steam. The steam then turns big turbines, which are essentially loops of wire in magnets.

Here's a good diagram of how the electrical generators work,
by spinning wire inside a magnetic field. Source: Macau Communications Museum

Ta da! Therein lieth the problem - how to get this turning energy without also creating more dangerous garbage than you get out of Parliament House. Cleaner sources that do the same thing include wind, dams, geothermal and waves, all adapted to turn wires. Solar works differently, we'll get into that later.

The particular type of power that comes from most power stations is alternating current, called AC for short. This is because the electrons first go one way, then turn around and come back. Australian electricity has a frequency of 50 Hertz, which means it goes back and forth 50 times a second. These jazzed-up electrons, like lemmings on speed, transfer their energy to your TV and microwave to give you the modern conveniences that make life worth living. The other type of current is DC (direct current), where the electrons only go one way. Batteries have DC elecricity.

But clearly the best use of alternating current and direct current is the delivery of rock!

So here it is in short: Moving electrical charges make a magnet, and moving magnets make electricity. Coz I'm TNT!


  • Halliday, D., Rescnick, R. & Walker, J. (1997), Fundamentals of physics: 5th edition, John Wiley & Sons , New York.
  • This website shows how generators work.
  • Be sure to play with this thing and generate all the electricity you want.
  • Here's a treatment of it with more diagrams.
  • And this page is also good, with more equations.


Who hasn't wondered about how warp drive works, or how you can teleport from one spaceship to another, or how Spock's ears got so pointy? Well Lawrence Krauss is not one of those people who hasn't. Lawrence is the author of several books (bestselling books - as he reminded us), most notably for this discussion is "The Physics of Star Trek".

Lawrence goes through heaps of topics in his book, but in our interview we only had time for a few of them. One really interesting topic that came up, is how you might teleport a person. How much information do you need to know in order to remake them? If you only need to know the relative location of all your neurons (along with a body shape that is roughly correct) then the teleporter might be possible. On the other hand, if you need to know the location of all the electrons and quarks, then forget about it. You shouldn't get in any such machine, since by the Heisenberg Uncertainty principle, you can't possibly get that information. The next time some door-to-door guy tries to sell you the latest and greatest teleporter, be sure to ask him about whether it comes with a Heisenberg compensator as standard. And don't forget the warning given by Douglas Adams:

I teleported home one night
With Ron and Sid and Meg,
Ron stole Meggie's heart away
And I got Sidney's leg.
- The Hitchhiker's Guide to the Galaxy

Here's Werner Heisenberg himself - he's uncertain if he'll ever be on a postage stamp.
Problem solved! Source: Wikipedia.

But when all is said and done, this pic really shows what the perks of writing a Star Trek book really are - cooking pizza with Captain Kirk.

Lawrence was explaning the concept of wormholes to Bill, using pizza. You can get the whole story on the video "How William Shatner changed the world". It's pretty good.


  • Guess... that's right! Read Lawrence's book: Krauss, Lawrence (1995), The physics of Star Trek, Harper Collins.
  • Or watch Star Trek.
  • You can find a whole stack of info about Lawrence on his website - including all his best-selling books, journal articles, lectures, photos, and his bio.

Quiz Refs:

Oops. Mistakes we shouldn't have made but did anyway:

  • Anthony is mortified that he made such a nerd faux pas as to call the faster-than-light drive on the Enterprise a 'hyperdrive'. It is of course a "warp drive". Anthony's excuse is that he is more of a Star Wars nerd (at least until Jar Jar Binks, out-of-control CGI, incoherent storylines, wooden acting, midochlorians and sickening child actors appeared), where they do call it hyperdrive.
  • When the others asked Anthony about why we use AC instead of DC if it's so dangerous, he forgot one important reason. Using AC lets you use transformers, and really where would we be without Jazz and Bumblebee and Prime and the gang? Seriously though, transformers are the things you plug into the wall to charge your phone or laptop. They don't work with DC current.
  • For the quiz bonus question (after question #1), Chris merely took the proportions of elements in the Earth's Crust and then took into account that 71% of the Earth's surface is ocean. But, he disregarded the organic content! After Anita mentioned carbon, Chris had a feeling that carbon should be near the top because of all the life slime sitting on the Earths' skin. We couldn't find info on the interwebs for the amount of overall biomass on the Earth's surface, but our opinion is that carbon would still be outplaced by Hydrogen & Oxygen (from the ocean's H2O) and probably Silicon (which make up most of our deserts and coastlines), but maybe not Aluminium.


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