NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

As LED is dimmed, what unique change occurs to this light source?

1. Increases in efficacy

2. Changes color

3. Becomes brighter

4. Generates more heat

The correct answer is: Increases in efficacy

When LED lighting is dimmed, a unique change that occurs is that the efficacy of the light source typically increases. Efficacy, which is the measure of how much light (lumens) is produced per unit of energy (watts) consumed, improves because the LED operates in a more efficient part of its performance curve when dimmed. As less energy is supplied to the LED, it converts energy into light more efficiently, ultimately resulting in higher lumens per watt. This characteristic is particularly beneficial in applications where energy savings and reduced heat generation are desirable. Dimming LEDs not only contributes to better energy efficiency but also leads to an extended lifespan of the lighting fixtures since operating at lower wattage reduces thermal stress on the components. While it is possible for LEDs to change color (notably, warm up) as they are dimmed due to the nature of some LED technologies, this is not a universal rule and isn't the primary change associated with dimming. LEDs do not become brighter when dimmed, and they generally produce less heat or heat at a lower rate when less power is supplied. Thus, the increase in efficacy stands out as the correct and significant change that occurs when LED lighting is dimmed.