Are high and low beams separate bulbs?
This is a great question since depending on the vehicle and manufacturer the lights can be configured in different ways. This can be a concern if you find your headlights are not working, since you need to know what type of bulbs to but to replace them with properly. Since the lens in modern headlights is separate from the bulbs this present a problem when replacing a lens for damage such as discoloration or from an impact.
Cars are built using single or dual filament bulbs. Older cars with single lights had dual filament bulbs that housed both the low beam and high beam light elements in a single bulb housing. These vehicles had two headlights total on the front one on each side. Then the design moved to individual bulbs which were single filament elements with a specific purpose of either a low or high beam light. These bulbs were arranged four total to the front of the car and configured either side by side on one on top of the other. The element in these bulbs work in a similar fashion to a household incandescent bulb. You may be even wondering how headlights work in general.
The adjust of the main beam of light from each of these light types is aimed or directed at different angles to improve the distance and angle of light beam reflected onto the road ahead of a vehicle. If the vehicle has a single headlight bulb (not the lens or reflector, but the actual bulb) then the bulb will have a dual filament internally which, when provided with battery power, will cause electrical current to flow through the element similar to the heating grid in an electric oven or a hair dryer. In the case of the bulb, it will cause it to glow.
In a separate light system where the low and high beam units are separate bulbs, each has only one filament and will illuminate when power is applied. Modern vehicles us one or more bulbs housed in a reflector assembly that appears to be one headlight unit. Keep in mind that there are also high intensity lights and LED lights as well used in these applications.
A concern that is often noted as well is when the headlight appears dimmer than the other, as if the dim light were about to blow out. So get your lights checked, replaced, and adjusted to see what's on the road ahead.
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