Applications of good conductors in everyday life :

Metals are good conductors of heat, therefore cooking utensils, kettles, irons, boilers, are always made up of iron, copper, Aluminum, or their alloys.

Think

1. Copper though a good conductor of heat is not used for cooking

2. Aluminum is preferably used for utensils, motor car engines, pistons, and cylinders

3. Mica sheet is placed between the filaments of electric irons.

4. Bad conductors of heat are also bad conductors of electricity. Find exceptions to this statement

 

Applications of bad conductors in everyday life :

Things which are bad conductors of heat are used as insulators. In same occasions it is important (1) to prevent heat loss from a hot body (2) to prevent heat from entering cold body.

1. The handles of saucepans, teapots, kettles, etc, are always made from substances like wood, plastic, etc, to prevent heat from entering the hand so that it can he held comfortably

2. Air is a poor conductor of heat, this is why heat from our bodies does not escape easily to the atmosphere

3. Fur, wool, cotton wool, cork, feathers, sawdust, trapped air in birds’ feathers etc. act as good insulators.

Fur and feathers keep most animals and birds during winter

Birds flutter their feathers in cold weather to trap air between their feathers

Woolen clothes keep as warm during winter

In cold countries, glass windows in houses are double paned

4. Refrigerators, ice boxes, ovens, solar heater panels and connecting pipes are made of double walls with filling of cork, air, cotton wool or polyurethane in between their walls.

5. Quilts are always filled with either cotton or foam

The use of a non conducting material to reduce heat from escaping is called lagging

Activity F

Look around you and make a list of items which have been insulated and how the insulation has been done.

Activity G

• Hold a piece of copper wire gauge over a Bunsen burner.
• Turn the gas on and light the gas under gauge
• Turn the gas off.
• Now again turn the gas on and light the gas above the gauge

Write your observations and justify

Search for information about Davy’s Safety Lamp used in mines. Why does the gas burn only inside the wire gauge? Why is such a lamp safe in a coal mine?