Topic Menu

Cyber-chess a chess instruction site

Questions on Expansion and Contraction

Q6. Below is a diagram of a simple fire alarm.

 

Briefly explain how it works. (Hint: brass expands more than iron when they both undergo the same temperature rise).

In a fire situation, the temperature would rise. This would case the bimetallic strip to expand. As the brass expands more than the iron for a given temperature rise, the strip would curve downwards (the longer brass section making the outer part of the curve). It would touch the contact, complete the circuit and the bell would ring.

(6 marks)