Quote:
Originally Posted by 1975300D
Ashedd, power in watts is the square of the voltage divided by the resistance.
P = Vē/R
So, if the voltage say is 10, and the resistance was say, 65 ohms - like the fuel gauge - then the wattage would be 1.5. Thus, for the wattage to be 5, then the resistance would have to be 20 ohms.
Does this makes sense?
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Not sure if this is what you are asking, but:
A 5 watt resistor is rated as such because that is the max amount it can safely pass. Using real-life numbers, the voltage is going to be more like 14 with the ohmic value of the resistor being 68, the current is going to be something above 2 watts. You might be able to get away with a 2.5 watt rated resistor, but you'd be bumping up against its max rating. Makes more sense to put in a 5 watt if available, doesn't it?