Magnetization

The Single Stroke Method

Creating a magnet.

You can turn an iron bar or needle into a magnet by stroking it 30 to 40 times with one pole of a bar magnet in the same direction.
Image 1

Key Points

  1. Always stroke from one end to the other in a single direction.
  2. Lift the magnet high at the end of each stroke before repeating.
  3. The starting end gets the same pole as the stroking pole.
  4. The finishing end where you lift the magnet gets the opposite pole.

Olympiad Fact

If you stroke an iron bar from left to right using a North pole, the left end becomes a North pole and the right end becomes a South pole!

Molecular Alignment

Straightening the field.

Inside an unmagnetized iron bar, tiny atomic regions called 'magnetic domains' point in random directions. Magnetization lines them all up in one direction.
Image 1

Key Points

  1. Every magnetic metal contains billions of tiny magnetic domains.
  2. Randomly jumbled domains cancel out, giving zero magnetism.
  3. Aligned domains pointing the same way create a strong magnet.
  4. Heat or hammering jumbles the domains back into disorder.

Olympiad Fact

Once every single internal domain in an iron bar is completely aligned, the magnet reaches 'magnetic saturation' and cannot get any stronger.

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