Transducers are electrical devices which convert energy from one form to another. Normally, these devices deal with energies like electrical, mechanical, chemical, thermal, electromagnetic, acoustic and many other.
Common examples include microphones, loudspeakers, thermometers, and antennas; all are transducers that transform one type of energy into another.
In transducers, the efficiency is considered to be an important factor. Transducer efficiency can be defined as the ratio of power output to the total input power. If F represents the power input and P represents the output power, then the efficiency is given by E= P/F and this ratio ranges between 0 and 1.
However, no transducer is 100% efficient and some power is always lost in the process of conversion. Usually, this power is lost in the form of heat.