Which one of the following transducers requires power supply for its operation?

The correct answer is option 4):(Thermistor)

Concept:

Thermistor:

• A thermistor is a semiconductor device that is a type of passive transducer in which variation in temperature causes a corresponding change in resistance. 
• The thermistor is a passive transducer
• It needs an external power supply for its operation

Additional Information

• A transducer is a device that is used to convert a physical quantity into its corresponding electrical signal i.e. the input is non-electrical and is converted into its corresponding electrical signal.

Input can be: Force, Displacement, Pressure, sound, voltage, or current

Output can be Resistance, capacitance Inductance, stress, strain Heat.

 Active transducers:

• Active transducers are those which do not require any power source for their operation.
• They work on the energy conversion principle.
• They produce an electrical signal proportional to the input (physical quantity).
• Piezoelectric, thermocouple, and photovoltaic cell transducers are some examples of active transducers.

​Passive transducers :

• Transducers which require an external power source for their operation is called passive transducer.
• They produce an output signal in the form of some variation in resistance, capacitance, or any other electrical parameter, which then has to be converted to an equivalent current or voltage signal.
• LVDT, strain gauge, RVDT, etc are examples of passive transducers.