What type of pressure can be applied to crystals to create a potential difference?

When discussing the application of pressure to crystals to create a potential difference, the correct answer relates to the physical phenomenon known as piezoelectricity. This phenomenon occurs when mechanical stress is applied to certain materials, specifically crystals, causing them to generate an electric charge.

Bending pressure, or flexural stress, is particularly effective for this purpose as it causes a deformation in the crystal structure that directly influences the distribution of electrical charges within the material. When a crystal is bent or flexed, the internal arrangement of its molecules shifts, leading to a separation of positive and negative charges. This separation creates a potential difference across the material.

In contrast, while other forms of pressure, such as shear, tensile, and impact pressure, can also stress materials, they do not necessarily induce the same uniform distribution of forces across the crystal lattice that bending pressure does, making bending the most relevant type for generating a significant potential difference in piezoelectric materials.