• Question: How do magnets work?

    Asked by rwariamadinosaur to Alan, Caspar, Diana, Murray, Sarah on 17 Mar 2011 in Categories: .
    • Photo: Caspar Addyman

      Caspar Addyman answered on 14 Mar 2011:

      Strangely enough they work by electricity. This is relatively easy to understand when the magnet is an electromagnet (like inside stereo speakers) that runs on electricity but it is is a lot harder to understand for bar magnets or the earth which is the biggest magnet around (even bigger than Sarah Thomas’s magnet the size of an elephant!) And incidently which is why all other magnets have a north and a south pole (rather than say a trunk and a tail).

      Michael Faraday (who used to be on £20 notes) discovered that whenever an electric current flows, it makes a circular magnetic field around itself. LIke this

      So if you arrange you wire in a circle you get all the arrows in those looops pointing the same way. LIke this

      And those are lines of magnetism. You get the same pattern in bar magnets because lots of the electrons orbiting its atoms also line up in the same angle as they orbit the atomic nucleus. And a moving electron is essentially exactly what electricity currents are. So they each make the same pattern of loops of magnetism and once you add lots and lots of them together you’ve got enough magnetism to make a magnet.

      I don’t know exactly how it happens inside the earth but the inside of the earth is mostly made of molten iron which conducts electricity and so something similar but on a massive scale must be happening.

      For a more cultural answer, watch this video. http://www.youtube.com/v/_P40uaZhIjk

    • Photo: Alan Winfield

      Alan Winfield answered on 16 Mar 2011:

      I think that the best way to understand how magnets work is by making an electromagnet. Get an ordinary nail and some insulated copper wire. Wrap the copper wire around the nail – perhaps 10 times – making a coil. If you now a compass and put it on the table near the nail+coil and connect the ends of the wire to a battery, you’ll see the compass needle move to point toward the electromagnet (instead of the North pole). Basically the current flowing through the wire and the coil creates a magnetic field – but it’s only temporary – if you disconnect the battery (which you’ll have to do anyway because the wire will get hot) the magnetic field disappears. What’s really interesting is that electro- magnetism works both ways. If you take a permanent magnet and move it through a coil of wire then you induce a current into a wire. One of my scientific heroes Michael Faraday worked all of this out in the 1820s: ideas that led to motors – which turn electricity into movement – and dynamos – which turn movement into electricity.

      So electricity and magentism are very closely connected. It’s the connection between them that led to one of the most amazing inventions ever (in my humble opinion) – radio. Another great Victorian called James Clerk Maxwell worked out the (very hard) maths called electromagnetic theory – which I had to learn when I was a student. Without electro- magnetism we wouldn’t have radios, TVs, satellites, sat nav, WiFi or mobile phones (and quite a few other things besides).

    • Photo: Sarah Thomas

      Sarah Thomas answered on 17 Mar 2011:

      Magnets are objects that produce magnetic fields and attract metals like iron, nickel and cobalt. The magnetic field’s lines of force exit the magnet from its north pole and enter its south pole. Opposite poles attract each other while like poles repel. Magnetic and electrical fields are related, and magnetism, along with gravity and strong and weak atomic forces, is one of the four fundamental forces in the universe.

      People use magnets to keep notes on refrigerator doors. They’re an essential part of technology items such as speakers, motors and computer hard disks. And credit cards carry account information on a magnetic strip.

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