The bimetallic strip in a fire alarm is made of two metals with different expansion rates bonded together to form one piece of metal. Typically, the low-expansion side is made of a nickel-iron alloy called Invar, while the high-expansion side is an alloy of copper or nickel. The strip is electrically energized with a low-voltage current. When the strip is heated by fire, the high-expansion side bends the strip toward an electrical contact. When the strip touches that contact, it completes a circuit that triggers the alarm to sound. The width of the gap between the contacts determines the temperature that will set off the alarm.
Answer:
![\rho = 1848.03 kg m^{-3}](https://tex.z-dn.net/?f=%5Crho%20%3D%201848.03%20kg%20m%5E%7B-3%7D)
Explanation:
given data:
density of water \rho = 1 gm/cm^3 = 1000 kg/m^3
height of water = 20 cm =0.2 m
Pressure p = 1.01300*10^5 Pa
pressure at bottom
![P = P_{fluid} + P_{h_2 o}](https://tex.z-dn.net/?f=P%20%3D%20%20P_%7Bfluid%7D%20%2B%20P_%7Bh_2%20o%7D)
![P = P_{fluid} + \rho g h](https://tex.z-dn.net/?f=P%20%20%20%3D%20P_%7Bfluid%7D%20%20%2B%20%5Crho%20g%20h)
![P_{fluid} = P - \rho g h](https://tex.z-dn.net/?f=%20%20%20P_%7Bfluid%7D%20%20%3D%20P%20-%20%5Crho%20g%20h)
= 1.01300*10^5 - 1000*0.2*9.8
= 99340 Pa
h_[fluid} = 0.307m
![99340 = 104900 + \rho *9.8*0.307](https://tex.z-dn.net/?f=99340%20%3D%20104900%20%2B%20%5Crho%20%2A9.8%2A0.307)
![\rho = 1848.03 kg m^{-3}](https://tex.z-dn.net/?f=%5Crho%20%3D%201848.03%20kg%20m%5E%7B-3%7D)