2. (a) Explain the principle of direct and inverse transducer with examples. (OR) Mb) Explain in detail about positive and negative temperature coefficient thermal transducers. [6 pts.]

### Direct and Inverse Transducers<br /><br />**Direct Transducer:**<br /><br />A direct transducer is a device that converts a non-electrical physical quantity directly into an electrical signal. The conversion process involves only one step, where the input physical quantity is directly transformed into an output electrical signal without any intermediate stages.<br /><br />- **Example:** A thermocouple is a direct transducer. It converts temperature differences directly into an electromotive force (voltage) using the Seebeck effect. When two different metals are joined at two junctions and exposed to different temperatures, a voltage is generated proportional to the temperature difference.<br /><br />**Inverse Transducer:**<br /><br />An inverse transducer performs the opposite function of a direct transducer. It converts an electrical signal into a non-electrical physical quantity. This type of transducer is used in applications where an electrical signal needs to be converted back into a form that can be perceived or utilized by other systems.<br /><br />- **Example:** A loudspeaker is an inverse transducer. It converts electrical audio signals into sound waves. The electrical signal causes the speaker diaphragm to move, creating pressure waves in the air that we perceive as sound.<br /><br />### Positive and Negative Temperature Coefficient Thermal Transducers<br /><br />**Positive Temperature Coefficient (PTC) Thermal Transducers:**<br /><br />PTC thermal transducers have a resistance that increases with an increase in temperature. These materials are useful in applications where it is necessary to detect or control temperature changes.<br /><br />- **Example:** PTC thermistors are commonly used as overcurrent protectors and self-regulating heating elements. As the temperature rises, their resistance increases, which reduces the current flow and prevents overheating.<br /><br />**Negative Temperature Coefficient (NTC) Thermal Transducers:**<br /><br />NTC thermal transducers exhibit a decrease in resistance as the temperature increases. They are widely used for temperature sensing and measurement due to their high sensitivity to temperature changes.<br /><br />- **Example:** NTC thermistors are often used in temperature sensors for automotive, consumer electronics, and industrial applications. As the temperature increases, the resistance decreases, allowing more current to pass through, which can be measured and correlated to the temperature.<br /><br />Both types of thermal transducers are essential in various applications, providing accurate temperature measurements and control mechanisms in electronic circuits and systems.