Take a sewing needle. Rub it with a bar
magnet several times always moving the
magnet in the same direction. Does the
needle get magnetised ? You may find that
the needle always acts like a magnet. With
the help of a magnetic compass you can
identify the north and south poles of the
needle. Pin a red coloured foam ball to
South Pole and white ball to North Pole of
the needle; then drop it in a bowl of water,
it floats. (Fig-9)
Answers
Answer:
Rub the magnet against the sewing needle at least five times. (If you are using a weaker magnet, such as a flat refrigerator magnet, rub the needle at least a dozen times.) Always rub the magnet in the same direction against the needle. Your needle should now be magnetized.
Now cut off about one quarter inch of the cork from one of the ends, making a small cork disk that is about one-quarter-inch tall.
Laying the cork disk on a flat surface, carefully push the needle through the side of the disk by using the pair of pliers. Push the needle all the way through the disk so that about the same amount of needle shows on either side of the disk.
Fill a wide cup, drinking glass or bowl with at least one inch of water.
Put the cork disk (with the needle) on the water in the cup. Try to keep the disk floating in the center of the water, away from the sides of the cup. What does the needle do? When it stops moving, what direction does it point toward?
Does your homemade compass seem to work well? How is it limited in its use?
Extra: Find out what direction north is in your location. Did your needle point in that direction? (You can use a real compass, an atlas or smartphone map for this.)
Extra: Put a magnet next to your compass. What happens to the needle as the magnet is moved close to it? How close does the magnet need to be to affect the compass? You could also try this with a steel object (such as a nail or possibly the pliers).
Extra: If you have magnets with different strengths, such as a flat refrigerator magnet and a rare earth magnet, try making multiple compasses using the different magnets to magnetize the needles. How well do the different compasses work compared with one another?
Extra: There are other ways you can make an inexpensive magnetic compass at home or while you are outdoors. For example, instead of using a piece of cork, you could try using a small leaf and setting the needle on top of the leaf while it floats in a still pool of water. How does a compass made using a leaf compare with one made using a piece of cork? How else could you make a magnetic compass?
Observations and results
Did the needle in your homemade compass align itself along the Earth's north and south poles?
When you rubbed the magnet against the sewing needle, you magnetized the needle, effectively making it a weak, temporary magnet. Because magnets interact with one another (pushing against one another or pulling one another together), the magnetized needle can interact with Earth's magnetic field. Although Earth's magnetic field is relatively weak, it should have clearly affected the needle because the needle was allowed to freely float in the cork disk on the water. Specifically, once it stopped moving, the needle should have aligned itself along Earth's magnetic field, lining up along the north/south axis. This means that one end of the needle should have pointed north, while the other pointed south. The same end should have always pointed the same direction. (You can do some more research to figure out how to make a compass that always has the needle's tip point a specific direction—either north or south.)
Explanation: