What property of a phototransistor determines its function?

The function of a phototransistor is determined by its light sensitivity. Phototransistors are semiconductor devices that operate like regular transistors but are specifically designed to be sensitive to light. When light photons strike the junction of the phototransistor, they create electron-hole pairs, enabling current to flow through the device. This light sensitivity is the key characteristic that allows phototransistors to convert light energy into electrical energy, making them essential in applications like light detection, optical communications, and automatic lighting systems.

While electrical resistance, capacitance, and inductance are important properties in the context of various electronic components, they do not define the operating principle of a phototransistor. Electrical resistance might influence the performance of the circuit the transistor is part of, but it doesn’t dictate how the phototransistor reacts to light. Capacitance and inductance pertain more to how components store and release energy, rather than their function in response to light. Hence, light sensitivity is the defining property that determines how a phototransistor operates.