Describes the property of certain materials to create a voltage when they are mechanically deformed.

• A. Piezoelectric effect
• B. Ferroelectric effect
• C. Thermoelectric effect
• D. Photoelectric effect

Answer: (A)

The main idea here is the piezoelectric effect: certain materials generate an electrical voltage when they are mechanically deformed. This happens because their crystal structure lacks a center of symmetry, so when you apply stress (compressing, twisting, etc.), the internal electric dipoles do not cancel out. The result is a net surface charge that creates a measurable voltage. Many piezoelectric materials, like quartz or certain ceramics, are used in sensors and actuators for this reason, and they can also work in reverse—applying a voltage makes them physically deform.

Ferroelectric materials involve spontaneous polarization that can be switched by an electric field, which is related but not the same as producing voltage from mechanical stress. The thermoelectric effect is about voltage generated from a temperature difference, not mechanical deformation. The photoelectric effect involves emission of electrons when light hits a material, which is unrelated to mechanical stress.