What type of device operates on the photoelectric principle?

The photoelectric principle refers to the phenomenon where electrons are released from a material, typically a metal, when it absorbs light or electromagnetic radiation. A device that operates on this principle is a photoelectric cell, commonly known as a photodiode or photovoltaic cell.

Photoelectric cells convert light energy directly into electrical energy by utilizing this principle. When light strikes the cell, it excites electrons, creating an electric current that can be used to power devices or charge batteries. This characteristic makes photoelectric cells essential components in various applications, such as solar power systems, light sensors, and automatic lighting controls.

In contrast, the other devices listed do not operate on the photoelectric principle. A transformer relies on electromagnetic induction to transfer electrical energy between circuits, capacitors store and release electrical energy but do not operate on light, and inductors store energy in a magnetic field generated by electrical current. Thus, the only correct application of the photoelectric principle is found in the photoelectric cell.