Fun with Magnets - Standard 6 - General Science - Balbharati
15. Fun with Magnets
Exercise
Q. 1 How will you do this?
(a) Determine whether a material is magnetic or non-magnetic.
Take a magnet and bring it near the object. If the object is attracted to the magnet, it is magnetic (for example iron, nickel, cobalt). If it is not attracted, it is non-magnetic.
(b) Explain that a magnet has a certain magnetic field.
Place iron filings on a sheet of paper and pass a magnet under the paper. The filings arrange themselves along lines that show how the magnetic force acts. These lines indicate the magnet's magnetic field (the space around the magnet where magnetic effects are felt).
(c) Find the north pole of a magnet.
Suspend the magnet by a thread so it can turn freely. The end which points to the north direction is the magnet’s north pole (N). Alternatively, bring a compass near the magnet: the north-pointing end of the compass needle (which itself is a small magnet) will be repelled by the magnet’s north pole and attracted by its south pole, helping identify the poles.
2. Which magnet will you use?
| Situation | Magnet to use (answer) |
|---|---|
| (a) Iron is to be separated from trash. | An electromagnet. |
| (b) You are lost in a forest. | A bar magnet. |
| (c) A window shutter opens and shuts continuously in the wind. | A permanent magnet. |
3. Fill in the blanks with the appropriate word.
(a) If a bar magnet is hung by a thread tied at its centre, its north pole becomes steady in the direction of the north Pole of the earth.
(b) If a bar magnet is cut into equal pieces by cutting it at right angles to its axis at two places, 3 bar magnets are formed, and a total of 6 poles are formed.
(c) There is repulsion between the like poles of a magnet, and attraction between its opposite poles.
(d) When magnetic material is taken close to a magnet, the material acquires induced magnetism.
(e) If a magnet attracts a piece of metal, that piece must be made of magnetic material or iron.
(f) A magnet remains steady in a north-south direction.
4. Write the answers in your own words.
(a) How is an electromagnet made?
An electromagnet is made by winding an insulated copper wire around an iron core (for example a nail) and passing electric current through the wire. The current produces magnetism in the iron core and the nail behaves like a magnet while the current flows. When the current is switched off, the magnetism disappears — thus an electromagnet is a temporary magnet.
(b) Write the properties of a magnet.
- A magnet attracts magnetic materials such as iron, nickel and cobalt.
- A magnet has two poles — a north (N) and a south (S) pole; magnetic force is strongest near the poles.
- Like poles repel each other; opposite poles attract each other.
- A freely suspended magnet aligns itself in the north-south direction.
- If a magnet is cut into pieces, each piece becomes a smaller magnet with its own north and south poles.
- Magnetism can be induced in magnetic materials placed near a magnet (induced magnetism).
(c) What are the practical uses of a magnet?
- Pin holders and cupboard door magnets (permanent magnets).
- Electromagnetic cranes in scrapyards and ports to lift heavy iron pieces.
- Electric bells, speakers, and motors that use electromagnetism.
- Compasses for finding directions.
- Maglev trains that use magnetic repulsion to reduce friction and travel at high speed.
- Data storage media (hard disks, magnetic strips on cards) use magnetic materials to store information.
