Activity . Take an aluminium or copper wire. Clamp this wire on a stand, as shown in Fig. .
. Fix a pin to the free end of the wire using wax. Heat the wire with a spirit lamp, candle or a burner near the place where it is clamped. What do you observe after some time?
Note your observations. Does the metal wire melt? The above activity shows that metals are good conductors of heat and have high melting points. The best conductors of heat are silver and copper.
Lead and mercury are comparatively poor conductors of heat. Do metals also conduct electricity? Let us find out. Figure .
Figure . Figure . Figure . Figure .
Metals are good conductors of heat. You must have seen that the wires that carry current in your homes have a coating of polyvinylchloride (PVC) or a rubber-like material. Why are electric wires coated with such substances? What happens when metals strike a hard surface?
Do they produce a sound? The metals that produce a sound on striking a hard surface are said to be sonorous. Can you now say why school bells are made of metals?