• Question: what you do to make a magnet

    Asked by dantheman to Daniel, Jon, Louise, Sharon, Zoe on 22 Jun 2010 in Categories: .
    • Photo: Sharon Sneddon

      Sharon Sneddon answered on 22 Jun 2010:

      To make a magnet, all you have to do is encourage the magnetic domains in a piece of metal to point in the same direction. That’s what happens when you rub a needle with a magnet — the exposure to the magnetic field encourages the domains to align (line up). Other ways to do this using a piece of metal include: Placing it a strong magnetic field in a north-south direction OR Holding it in a north-south direction and repeatedly striking it with a hammer, physically jarring the domains into a weak alignment (DON’T TRY THIS AT HOME!!) or by passing an electrical current through it.

      The most common method of making magnets today involves placing metal in a magnetic field. The field places something called torque on the material, encouraging the domains to align. There’s a slight delay, known as hysteresis, between the application of the field and the change in domains — it takes a few moments for the domains to start to move.

      The magnetic domains rotate, allowing them to line up along the north-south lines of the magnetic field. Domains that already pointed in the north-south direction become bigger as the domains around them get smaller. Domain walls, or borders between the neighboring domains, physically move to accommodate domain growth. In a very strong field, some walls disappear entirely.
      The resulting magnet’s strength depends on the amount of force used to move the domains. Its permanence, or retentivity, depends on how difficult it was to encourage the domains to align. Materials that are hard to magnetize generally retain their magnetism for longer periods, while materials that are easy to magnetize often revert to their original nonmagnetic state.

    • Photo: Jon Copley

      Jon Copley answered on 22 Jun 2010:

      You can make a magnet out of a bit of the right kind of metal (like a paperclip), if you stroke an existing magnet over it in the same direction lots of times.

      But what if you don’t already have a magnet to start with?

      If you want to make one from scratch, get a piece of iron and a hammer. Lay the piece of iron down on something hard, and so that the iron object is pointing in a north-south direction (you can look at where the sun rises and sets to figure out where north and south are, because the sun rises in approximately in the east and sets roughly to the west).

      Then hit the piece of iron again and again with the hammer (this step can take quite a while – you have to keep going!).

      Iron is made up of tiny “mini-magnets”, but normally they’re all jumbled up, pointing in different directions. The whole piece of iron only becomes a magnet when all the mini-magnets in it are lined up the same way. When you hit the iron with your hammer, you are shaking up the mini-magnets in it – and then they settle lined up a bit better in the direction of the Earth’s magnetic field. So that can make the iron into a very weak magnet.

      In a way, though, you are still using another magnet to make your magnet here – you are actually using the Earth as another magnet.

    • Photo: Louise Dash

      Louise Dash answered on 22 Jun 2010:

      Some things are naturally magnetic, like lodestones, which were used as the first compasses.

      You can magnetize some metals, like iron, by rubbing it in the same direction with a magnet. This is because electrons in the metal have a property called “spin”, which all line up in the same direction to form a magnetic field.

      You can also make an electromagnet by winding some insulating copper wire around an iron nail and connecting the wire to a battery – the current through the coiled wire creates a magnetic field which magnetizes the iron.

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