The north pole of magnet P is brought near the north pole of magnet Q.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- The north pole of magnet P is brought near the north pole of magnet Q. What happens?
- The north pole of P is brought near the south pole of Q. What happens?
- A copper coin is brought near P. What happens?
- Two bars, A and B, look the same. One is a magnet, the other plain iron. The end of A pulls the middle of B strongly, but the end of B hardly pulls the middle of A. Which bar is the magnet?
Need a reminder? The key ideaShow
Every magnet has a north pole and a south pole. Like poles repel and unlike poles attract. A magnet attracts iron, nickel and cobalt, but not copper, aluminium or plastic. A piece of a magnet is a whole magnet, with two poles.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Like poles: they repel.
Step 2. (b) Unlike poles: they attract.
Step 3. (c) Copper is not a magnetic material, so nothing happens.
Step 4. (d) A magnet's poles are at its ends, and its field is very weak at its middle. A's end pulls B's middle, so A has a pole there: A is the magnet. B's end is plain iron and the middle of A has almost no field, so they hardly pull.
Answer: (a) repel. (b) attract. (c) no force. (d) A is the magnet.
Check. Only repulsion proves that both bars are magnets: iron is pulled by either pole, but never pushed.
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