Which of the following is not a transducer?

Options

A. Loud speaker
B. Amplifier
C. Microphone
D. All of these

Answer

To determine which of the following options is not a transducer, we need to understand the definition of a transducer and analyze each option given.

### Step-by-Step Solution:

1. **Understanding Transducers**:
- A transducer is a device that converts one form of energy into another. This can include converting sound energy into electrical energy, or vice versa.

2. **Analyzing the Options**:
- **Loudspeaker**:
- A loudspeaker converts electrical energy (from an audio signal) into sound energy (vibrations in the air). Therefore, it is a transducer.
- **Amplifier**:
- An amplifier takes low amplitude electrical signals and increases their amplitude. It does not convert one form of energy to another; it merely amplifies the electrical signal. Thus, it is not a transducer.
- **Microphone**:
- A microphone converts sound energy (vibrations in the air) into electrical energy (electrical signals). Therefore, it is a transducer.

3. **Conclusion**:
- Among the options provided, the amplifier is the only device that does not convert energy from one form to another. It simply amplifies the electrical signal. Thus, the answer is **amplifier**.

### Final Answer:
The device that is not a transducer is the **amplifier**.