The phenomenon of producing voltage by exerting pressure on a crystalline substance is known as what?

The phenomenon of producing voltage by exerting pressure on a crystalline substance is known as the piezoelectric effect. This effect occurs in certain materials, typically crystals, where an applied mechanical stress leads to the generation of an electrical charge. The molecular structure of these materials allows for the displacement of charge within the crystal lattice when pressure is applied, resulting in the creation of voltage.

This property is widely utilized in various applications, such as in piezoelectric sensors, actuators, and in devices like microphones and speakers where mechanical motion is converted into electrical signals, or vice versa. The piezoelectric effect is an essential principle in fields such as electronics, materials science, and engineering.

The other options describe different phenomena that do not relate to the generation of voltage through mechanical pressure on crystals. Electromagnetic induction involves the production of voltage through a changing magnetic field, chemical reactions pertain to changes in chemical compositions that can generate electricity (like in batteries), and the thermoelectric effect is related to the conversion of temperature differences into voltage. Each of these operates on principles distinct from the piezoelectric effect.