What phenomenon does the reverse piezoelectric effect refer to?

The reverse piezoelectric effect refers to the phenomenon where an applied electric field causes mechanical deformation in certain materials, particularly crystals. This means that when an alternating current is applied to specific piezoelectric materials, it induces physical changes in shape, such as expansion or contraction. The effect is fundamental to many applications, including actuators and sensors, where the conversion between electrical energy and mechanical energy is essential.

In the context of this question, the correct answer highlights the relationship between electric current and the mechanical movement of the crystals, which is a core aspect of understanding how piezoelectric materials function. Other options, while they touch on related concepts, do not accurately capture the specific interaction at play with the reverse piezoelectric effect. For instance, pressure dissolving crystals or heat generation from sound waves does not directly explain the linkage between alternating current and mechanical deformation. Similarly, capacitance level changes pertain more to the storage of electrical energy rather than the physical expansion or contraction associated with the applied electric field in piezoelectric materials.