When we look at a vehicle lighting system in operation, what we commonly think of as light, is actually heat coming from the bulbs in the system. When we pass elcectrical current through the filament of a bulb, this electricity can have one of the 3 effects of electricity on that filament:

  1. Chemical change.
  2. Heat.
  3. Magnetism.

The effect of electricity we are interested in here is heat. The electricity heats the filament up to white hot, and the filament becomes incandescent, or glows.

The term incandescent heat simply means glowing heat, and this is what we are seeing when we switch on a vehicle's headlamps.

» Course Glossary