Using diagram, explain how a bimetallic strip is used inan electric fire alarm.

A bimetallic strip is a crucial component in many devices, including electric fire alarms, due to its ability to bend and change shape in response to temperature variations. Here's a breakdown of how it works in an electric fire alarm:

1. Understanding the Bimetallic Strip

• A bimetallic strip consists of two different metals with different coefficients of thermal expansion bonded together.
• As the temperature rises, one metal expands more than the other, causing the strip to bend.

2. Function in Electric Fire Alarm

• When the surrounding temperature increases due to a fire, the bimetallic strip bends.
• This bending action can open or close an electrical circuit within the alarm system.

3. Diagrammatic Representation

Here's a simple diagram to illustrate the concept:

                            +-------------------+
                            |     Fire Alarm     |
                            |                   |
                            |   +-----------+   |
                            |   |    Bell   |   |
                            |   +-----------+   |
                            |        |          |
                            +--------|----------+
                                     |
                                   +-+-+     +----------------+
                                   |   |-----| Bimetallic    |
                                   |   |     |   Strip       |
                                   |   |-----|                |
                                   |   |     |                |
                                   |   |     | (Two metals)   |
                                   +---+     +----------------+
                                     |
                                 (Heat from fire)

4. Operation

• Normal Conditions: In normal temperatures, the bimetallic strip remains straight, allowing the electrical circuit to remain closed.
• Under Heat: If the temperature exceeds a certain threshold due to a fire, the strip bends and activates the alarm by breaking the circuit or triggering a switch that allows the alarm to sound.

Conclusion

The bimetallic strip effectively acts as a temperature sensor in fire alarms, mechanically responding to temperature changes to ensure safety by signaling the presence of heat from a potential fire.