Question 748 Deck Safety

The correct answer is D) the difference in thermal expansion of two dissimilar metals. Fire alarm system thermostats are actuated by the difference in thermal expansion of two dissimilar metals. As the temperature rises, the two metals expand at different rates, causing the thermostat to trigger the fire alarm system. This is a common mechanism used in fire alarm thermostats, as it provides a reliable and temperature-sensitive means of detecting and responding to fire hazards. The other options are incorrect because: A) smoke sensors detect the presence of smoke, but do not directly actuate the thermostat; B) an electric eye is not the mechanism used in a fire alarm thermostat; and C) pressure loss due to heated air is not the principle behind the thermostat's operation.