What effect is primarily responsible for generating electricity from mechanical stress?

The correct choice is the piezoelectric effect, which refers to the ability of certain materials to generate an electric charge in response to applied mechanical stress. This phenomenon occurs in materials like quartz and certain ceramics, where an external force causes a displacement of the charge distribution, leading to the formation of an electric field and voltage.

In practical applications, the piezoelectric effect is widely utilized in sensors, actuators, and energy harvesting devices, allowing mechanical movements, such as vibration or compression, to be converted into electrical energy. This effect is critical in various technologies, including microphones, pressure sensors, and even some types of energy-efficient light bulbs, where mechanical stress leads to the generation of electrical signals.

Understanding this mechanism is essential for fields that involve material science and electrical engineering, particularly when exploring alternative energy sources and innovative sensor technologies.