Conductors and Insulators

Conductors

              Solids which allow heat to pass through them are called good conductors of heat.

eg. Metals such as iron, copper, aluminium, silver, and mercury.

       Because of this property the cooking vessels and boilers are made of metals.

         Materials which do not allow heat to pass through them are called poor conductors of heat or insulators.

eg. Wood, glass, rubber, leather, plastic, mica, stone, marble and thermocole.

         The cooking vessels made of metals get heated up quickly. But their handles are made of poor conductors such as plastic or wood. All liquids and gases are poor conductors of heat. 

           The steel chair appears cooler to touch than a wooden chair because steel is a good conductors of heat energy at the same time wood is a poor conductor.

Uses of good conductors

              Some important uses of good conductors are listed below.

1. Cooking vessels are made of metals, so that the vessels get heated quickly and transfer the heat to the food being cooked.

2. Copper-bottom cooking vessels are used to save time and fuel because copper is a good conductor of heat.

3. Mercury is used in thermometers as it is a good conductor of heat.

4. The tubes used in automobile radiators are made up of copper which absorbs heat speedily from the hot water coming from the engine.

Uses of insulators (or) bad conductors

1. The handles of cooking vessels and the handles of heating iron are made of poor conductors or insulators like ebonite or wood.

2. woollen clothes keep us warm during winters by retaining the heat of our body. woollen clothes have fine pores which when filled with air is used to prevent the loss of heat.

3. Hot packs, hot water storage tanks are lined with wool, cork, fibre-glass or asbestos wool to prevent the best from escaping.

4. In cold countries the water pipes are covered with cotton to prevent the freezing of water.

5. An ice- box has double walls and the space between them is filled with materials like wool, cork or thermocole which are insulators.

6. Mud houses with thatched roofs keep cool in summer and warm in winter as compared to concrete houses. It is because the thatched roof contains large amount of trapped air. Similarly, mud is a bad conductor of heat.

7. In cold countries animals are generally covere with thick fur. The fur contains a large amount of air and acts as an insulator.