The conversion of part of energy into an unuseful form of energy is called……………

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the term that describes the conversion of part of energy into an unuseful form of energy.

2. **Defining Key Terms**:
- Useful energy: This is energy that can be harnessed to perform work or produce a desired effect.
- Unuseful energy: This refers to energy that cannot be effectively used to perform work, often dissipated as heat or sound.

3. **Identifying the Concept**: The process of energy changing from a useful form to an unuseful form is a common phenomenon in energy transformations.

4. **Recalling Relevant Definitions**: The term that describes this conversion is known as "degradation of energy." This means that as energy is transformed, some of it is lost in a form that cannot be used effectively.

5. **Final Answer**: Therefore, the conversion of part of energy into an unuseful form of energy is called **degradation of energy**.