Practical Application of Conduction of Heat

Practical Application of Conduction of Heat

(1) Ice box has a double wall, made of tin or iron. The space between the two walls is filed with cork or felt which are poor conductors of heat. They prevent the flow of out side heat into the box, thus keeping the ice from melting.

(2) Woolen clothes have fine pores filled with air. Air and wool are bad conductors of heat. Thus the heat from the body does not flow out to the atmosphere. Thus the woolen clothes’ keep the body warm in winter.

(3) In cold countries windows are provided with double doors. The air in the space between the two doors forms a non conducting layer and so heat cannot flow out from inside the room.

In hot countries as well, the windows are made with double doors. Heat can not flow in from outside because of the presence of air between the two doors.

(4) When a stopper, fitted tightly to the bottle is to be remained, the neck of the bottle is gently heated. It expands slightly on heating. Since glass is a bad conductor of heat, the heat does not reach the stopper. Thus it can be removed easily.

(5) Davy’s Safety Lamp: It is one of the most important applications of conduction of heat. The principle of Davy’s safety lamp can be understood from a simple example in which a wire gauze is placed over a Bunsen burner. The gas coming from the burner is lit above the wire gauze.

A flame appears at the top surface of the wire gauze. The gas coming out from the burner below the wire gauze does not get sufficiently heat for ignition. The reason is that the wire gauze conducts away the heat of the flame above it and so the temperature at the lower surface of the gauze does not reach the ignition point.

In Davy’s safety lamp, a cylindrical metal gauze of high thermal conductivity surround the flame. When this lamp is taken inside a mine, the explosive gases present in the mine are not ignited because the wire gauze in the form a cylinder conducts away the heat of the flame of the lamp. The result is that the temperature outside the gauze remains below the ignition point of the gases. In absence of the wire gauze the gases outside can explode.