In an experiment to demonstrate the mechanism of breathing by using a bell jar, two balloons in the bell jar and a rubber sheet tied to the open end of bell jar :
What does the rubber sheet tied over the open end of the bell jar represent ?

Answer

**Step-by-Step Solution:**

1. **Understanding the Experiment Setup**: In the experiment, a bell jar is used with two balloons inside it and a rubber sheet tied over the open end. This setup is designed to demonstrate the mechanism of breathing.

2. **Identifying the Components**: The two balloons inside the bell jar represent the lungs. The rubber sheet tied to the open end of the bell jar is crucial for simulating the breathing process.

3. **Function of the Rubber Sheet**: The rubber sheet acts like the diaphragm in humans. The diaphragm is a muscular structure that separates the chest cavity from the abdominal cavity and plays a key role in the breathing process.

4. **Mechanism of Breathing**:
- When the rubber sheet is pulled down, it increases the space inside the bell jar, which causes the balloons (lungs) to inflate as air is drawn in. This simulates inhalation.
- When the rubber sheet is pushed back to its original position, it decreases the space inside the bell jar, causing the balloons to deflate as air is pushed out. This simulates exhalation.

5. **Conclusion**: Therefore, the rubber sheet tied over the open end of the bell jar represents the diaphragm in the human body, which is essential for the process of breathing.

---