Bimetal strips are used for

Options

A. metal thermometer
B. opening or closing electrical circuits
C. thermomsats
D. All of the above

Explanation

### Step-by-Step Solution:

1. **Understanding Bimetal Strips**:
- Bimetal strips are made by joining two different metals that have different coefficients of thermal expansion. When the temperature changes, one metal expands more than the other, causing the strip to bend.

2. **Identifying Applications**:
- Bimetal strips are used in various applications due to their ability to convert temperature changes into mechanical displacement. We will analyze the options provided.

3. **Application in Metal Thermometers**:
- In metal thermometers, bimetal strips are used because they expand with temperature changes. The bending of the strip can be calibrated to indicate the temperature on a scale.

4. **Application in Electrical Circuits**:
- Bimetal strips can also be used to open or close electrical circuits. In appliances, they act as safety devices that prevent overheating by breaking the circuit when the temperature exceeds a certain limit.

5. **Application in Thermostats**:
- In thermostats, bimetal strips control the operation of heating and cooling systems. As the temperature changes, the strip bends and can activate or deactivate the system to maintain the desired temperature.

6. **Conclusion**:
- Since bimetal strips are used in metal thermometers, for opening or closing electrical circuits, and in thermostats, the correct answer is that they are used in **all of the above**.

### Final Answer:
Bimetal strips are used for **all of the above** (metal thermometers, opening or closing electrical circuits, and thermostats).

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