Correct Answer - Option 4 : Piezoelectric Crystal
The inverse transducer is defined as a device that converts an electrical quantity into a non-electrical quantity.
A piezoelectric crystal acts as an inverse transducer because when a voltage is applied across its surfaces, it changes its dimensions causing a mechanical displacement.
Note:
A piezoelectric sensor is a device that uses the piezoelectric effect to measure changes in pressure, acceleration, temperature, strain, or force by converting them to an electrical charge. It is used to measure displacement.
