Question

The transducers which do not need any external power source to produce output are known as

• A. Primary transducers
• B. Active transducers
• C. Passive transducers
• D. Analog transducers

Hint:

Remember: Active = Alone (can work by itself). Passive = Power required.

Answer 1

The Correct Option is B

Transducers are devices that convert one form of energy into another. They are broadly classified based on whether they require an external power source to operate. 1. Active Transducers (Self-Generating): Active transducers are those that develop their own electrical output (voltage or current) directly from the physical quantity being measured. They do not require any external auxiliary power. Examples include:

• Thermocouples: Produce a voltage proportional to a temperature difference.

• Piezoelectric crystals: Produce a charge when subjected to mechanical stress.

• Photovoltaic cells: Produce electricity from light.

2. Passive Transducers (Externally Powered): Passive transducers require an external power source to function. They work by changing a passive electrical property (like resistance, inductance, or capacitance) in response to the input. A common example is a strain gauge (Resistance changes, but you need a battery to measure it).

3. Summary: Because active transducers "generate" their own signal using energy from the input source itself, they are the ones that operate without an external power supply.