Properties of Magnets

Centers of Maximum Attraction

The power of poles.

Magnetic force is not uniform across a magnet. Attraction is strongest near the two ends—called the North Pole (N) and South Pole (S)—and weakest at the center.
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Key Points

  1. Iron filings stick heavily in thick clumps at the two poles.
  2. Almost no iron filings stick to the middle of a bar magnet.
  3. Poles sit slightly inside the ends, not at the very edge.
  4. Both the North and South poles have equal magnetic strength.

Olympiad Fact

If a bar magnet is rolled in a dish of iron filings, the filings cling densely to the two poles while leaving the center nearly bare.

The Directive Property

Finding the path.

A magnet suspended freely from a thread always comes to rest pointing in the geographic North-South direction because it aligns with Earth's magnetic field.
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Key Points

  1. The end pointing North is called the North-seeking pole (N).
  2. The end pointing South is called the South-seeking pole (S).
  3. Works only when the magnet hangs freely without nearby iron.
  4. Forms the working principle of every magnetic compass.

Olympiad Fact

Ancient travelers navigated across deserts and oceans by hanging a natural lodestone from a silk thread.

Law of Magnetic Poles

Attract vs Repel.

When two magnets are brought close together, unlike poles (N-S) pull toward each other, while like poles (N-N or S-S) push away from each other.
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Key Points

  1. Unlike poles attract: North pulls South (N-S).
  2. Like poles repel: North pushes North (N-N) and South pushes South.
  3. Magnetic force is a non-contact force that acts across empty space.
  4. The closer the two magnets get, the stronger the pull or push.

Olympiad Fact

Repulsion is the ONLY sure test of magnetism, because a magnet attracts both another magnet (opposite pole) and plain unmagnetized iron!

Poles Always Exist in Pairs

Inseparable ends.

You can never separate a North pole from a South pole. If a magnet is cut or broken in half, each piece immediately forms its own North and South poles.
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Key Points

  1. A single isolated North or South pole (monopole) cannot exist.
  2. Cutting a magnet into two pieces creates two smaller complete magnets.
  3. New opposite poles appear instantly at the freshly broken ends.
  4. Even a tiny microscopic grain of a magnet has both N and S poles.

Olympiad Fact

Because every magnet always has two opposite poles, scientists call a magnet a 'magnetic dipole'.

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