Understanding Transducers and Thermistor Properties

The question asks to identify the false statement among the given options concerning transducers and thermistors. Let's analyze each statement to determine its accuracy.

Transducer Definition and Function

• Statement 1: "A transducer is an energy conversion device."
• Analysis: This statement is true. A transducer is a device that converts energy from one form to another. For example, a microphone converts sound energy into electrical energy, and a loudspeaker converts electrical energy back into sound energy. This fundamental principle makes transducers essential in various measurement and control systems.

Strain Gauge as an Electrical Transducer

• Statement 2: "Strain gauge is an electrical transducer."
• Analysis: This statement is also true. A strain gauge is a type of transducer that converts mechanical strain (deformation) into an electrical signal, typically a change in resistance. When the material to which the strain gauge is attached experiences strain, the resistance of the strain gauge changes proportionally, allowing the measurement of force, pressure, tension, or weight.

Thermistor as a Variable Resistance Transducer

• Statement 3: "A thermistor is variable resistance transducer."
• Analysis: This statement is true. A thermistor is a type of resistor whose resistance is highly dependent on temperature. This property allows it to function as a transducer, converting changes in temperature into measurable changes in electrical resistance. Because its resistance varies significantly with temperature, it is accurately described as a variable resistance transducer used primarily for temperature measurement and control.

Thermistor Temperature Coefficient

• Statement 4: "Thermistors have negative temperature coefficient of resistance."
• Analysis: This statement is the false statement in the context of the question. While it is true that many common thermistors, known as NTC (Negative Temperature Coefficient) thermistors, exhibit a decrease in resistance as temperature increases, it is not universally true for all thermistors. There are also PTC (Positive Temperature Coefficient) thermistors, whose resistance increases as temperature rises. Since the statement generalizes to "Thermistors" without specifying NTC type, and PTC thermistors exist, the blanket statement that all thermistors have a negative temperature coefficient is incorrect. Therefore, this statement is false.

Conclusion

Based on the analysis, the statement that is false is "Thermistors have negative temperature coefficient of resistance" because thermistors can also have a positive temperature coefficient.