A device to change one form of energy into another form of energy is called a:

A device that changes one form of energy into another is called a transducer. Transducers function by converting various types of energy, such as mechanical, electrical, thermal, or electromagnetic, from one form into a different form. For instance, a microphone converts sound (mechanical energy) into electrical energy, while a speaker converts electrical energy back into sound. This ability to bridge different types of energy is crucial in numerous biomedical applications, such as in imaging devices, where light might be converted to electrical signals for processing.

In contrast, capacitors store electrical energy but do not convert energy types. Transformers are specifically used in electrical systems to transfer electrical energy between circuits, changing voltage levels but not transforming to a different energy form. Transistors are semiconductor devices that control electrical current but do not inherently change energy types. Thus, transducer is the most accurate term to describe a device that alters energy forms.