Name: A Laboratory Thermometer
Uploaded: 2019-07-19
Duration: 4 min 53 s
Description: We need a device to measure temperatures more accurately in laboratories. In this video, we introduce you to a device that will help us measure laboratory te...

Question

Give one example where expansion on heating is put to good use. Explain the working with the help of a labelled diagram.

Accepted Answer

Automatic fire alarm is works based on expansion on heating, which is put to good use. The fire alarm works on the principle that different solids expand differently for the same temperature. An automatic fire alarm consists of a bimetallic strip which has two different metals strips, iron and brass, bolted together firmly. Brass expands more than iron on heating. Therefore, when fire will reach this bimetallic strip, the brass will expand more, thereby bending it towards the iron strip.

In a fire alarm, a bimetallic strip is connected to an open circuit as shown in the figure. When the surroundings got fire, the strip become hot and expands and bend as shown in the figure. Due to this bending of the strip, the circuit for the electric bell is completed, and it starts ringing as the fire alarm. Once the strip cools down, it will return to its original shape, i.e., straighten up to break the circuit and stop the alarm.

Give one example where expansion on heating is put to good use. Explain the working with the help of a labelled diagram.

Important Questions on Heat and Its Effects

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