Electronics Engineering (ELEX) Board Practice Exam 2026 - Free ELEX Exam Practice Questions and Study Guide

The main function of a photoresistor, also known as a light-dependent resistor (LDR), is to change its resistance based on light intensity. When light falls on the photoresistor, its resistance decreases, allowing more current to pass through it. Conversely, in the absence of light, the resistance increases, reducing the current flow. This property makes photoresistors highly useful in various applications, such as in light-sensing circuits, automatic streetlights, and other devices that require light sensitivity.

The other choices present potential functions relevant to electronics but do not accurately describe the core function of a photoresistor. Temperature measurement is typically accomplished with thermistors or temperature sensors, while electrical charge storage is a role fulfilled by capacitors or batteries. The conversion of light into energy is primarily associated with photovoltaic cells rather than photoresistors, which do not generate energy but rather respond to light by altering their resistance.