In a mercury thermometer, the level of mercury rises when its bulb comes in contact with a hot object.What is the reason for this rise in the level of mercury ?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Thermometer Structure**: A mercury thermometer consists of a glass tube with a bulb at one end filled with mercury. The tube is narrow, allowing for precise measurements.

2. **Heat Transfer**: When the bulb of the thermometer comes into contact with a hot object, heat from the hot object is transferred to the mercury inside the bulb.

3. **Expansion of Mercury**: As the mercury absorbs heat, its temperature increases. According to the principles of thermal expansion, when a substance is heated, it tends to expand.

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