Electronics Engineering (ELEX) Board Practice Exam

The output of a photoresistor, also known as a light-dependent resistor (LDR), is characterized by its inverse relationship with light intensity. As the intensity of light increases, the resistance of the photoresistor decreases, allowing more current to flow through it. Conversely, as the light intensity decreases, the resistance increases, resulting in less current flow. This behavior means that the output signal varies inversely with the amount of light striking the device.

Photoresistors work based on photoconductivity, where the resistance changes in response to the amount of photons absorbed by the semiconductor material. This characteristic makes photoresistors particularly useful in light-sensing applications, where the ability to vary output in conjunction with light changes is essential.

The other options do not accurately describe how a photoresistor operates. A constant output would imply no change with varying light conditions, while a decrease with increased light suggests a direct, rather than inverse, response. Random fluctuations would not portray the predictable nature of a photoresistor's output, which directly correlates with light intensity in a consistent manner.