NCERT 10th Class Science Chapter Magnetic Effect of Electric Current
Magnet was first discovered some 5,000 years ago in Magnesia. It could attract small pieces of iron towards it and had directional property i.e. when suspended freely, it always points in north-south direction. There is a true story behind its discovery.
(A) Discovery of Magnet: There was a shepherd boy named Magnaus in the town Magnesia in Greece. He had wooden stuff attached to iron sole. One day he left it in a mine. When he came back, the iron sole was firmly attacked to the roof. He got terrified and thought it to be work of some evil spirit or ghost. The roof was actually an iron ore (Fe3O4) magnetite. This first discovered magnet was called magnetite or natural magnet. It points in a particular (N–S) direction. It is also called loading stone which has now been changed to lode stone.
Gilbert made detailed study of magnets and their properties. Magnets are essential parts of all generators used for the production of electricity. They also form essential parts of electric motors, TV., radio, stereos and large number of instruments.
(B) Properties of Magnets
(i) It attracts small pieces of iron towards it i.e. it has attractive property.
(ii) When suspended freely, it always points in north south direction. Thus magnet possesses directional property.
(C) Properties of magnet: William Gilbert of England was the first person to study and record the properties of a magnet in a book titled "The magnet". Let us study some important properties of magnets.
(D) Poles of Magnet: The two ends of a magnet where the magnetic force is greatest are called the poles of the magnet. Each magnet has two poles magnetic north pole and magnetic south pole.
Spread out some iron filings over a sheet of paper. Now, move a bar magnet over the filings taking care that all parts of the magnet move through iron filings and Observe how the iron filings are distributed all over the magnet. You will notice that most of the iron filings cling near the ends of the magnet while there are a few iron filings near the middle (see figure).
Repeat the experiment with a horse-shoe magnet You will find that all magnets have maximum attractive power at their poles. This activity shows another fact about the attractive property of magnets.
(E) Directional Property: The end of the magnet that points towards the North is called the North Pole (N-Pole) and the other end of the magnet pointing towards the South is called the South Pole (S-Pole), A magnet always points in the north-south direction when suspended freely.
Take a bar magnet and suspend it freely as shown in figure or float it on a block of wood in water. The magnet comes to rest afte