Thread: Why do my lights get brighter when I rev the engine?
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Old 09-01-09, 08:05 PM   #43
thefallenangel
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Default Re: Why do my lights get brighter when I rev the engine?
Quote:
Originally Posted by BillyC View Post
A 55W bulb, is a 55W bulb... no matter how bright or dim it is... put 12v through it and it'll draw about 4.6 Amps.

[Edit] Just to add... what makes a bulb 55W is a factor of its restistance, and the voltage that is applied to it, as demonstrated by the simple equation: I=V/R.

The headlight is rated 55W at 12V... which means its resistance is approximately 0.2 Ohms. Since the bulb's resistance is constant (for the sake of argument), only a reduction in voltage will cause the current to drop.

So for the bulb to get dimmer... it must have a varying voltage put through it. Enough... I'm bored now.
Simplest things to remember is fundamental electrical formulas.

V=IR I=V/R R=V/I. (Ohm's triangle) and P=IV(and the cos of the angle but it's generally ignored) or P=V^2R. As long as you know those you should be fine.
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