A transducer is a device that converts one form of energy into another. For example, a microphone transforms sound waves into electrical signals, while a speaker does the opposite by converting electrical signals back into sound. Transducers are essential in various applications, including audio equipment, medical devices, and industrial sensors. Transducers can be classified into two main types: active and passive. Active transducers generate their own electrical energy, like solar cells, while passive transducers require an external power source to operate, such as thermistors. These devices play a crucial role in enabling communication and measurement in technology and science.