Topic Menu

Cyber-chess a chess instruction site

Questions on Expansion and Contraction

Q7. 

(a) What is a thermostat?

A thermostat is a component which senses the temperature of a system so that the system's temperature is maintained near a desired setpoint. Thermostats are used in any device or system that heats or cools to a set-point temperature.

A thermostat is used in electric haircurling tongs. Below is a diagram of such a thermostat.

(b) What happens if the tongs get too hot?

If the iron is too hot the bimetallic strip curves upwards and breaks the heater circuit because it is no longer touching the contact.

(c) What happens later when the tongs cools again?

As it cools the bimetallic strip straightens and the circuit is complete again, making the heater warm the iron.

(4 marks)