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geraldh said:Hello people
I am a newbee.
All I just want to know how do I calculate what Resistor will I need.
Example: I got a 12v DC Adapter with a 3v Bulb. Now I want to put in a resistor to bring down the Voltage so the bulb can glo and not blow.
Thanks.
Painandsuffering said:Hey nigel nice usage of watts law and ohm law but don't forget he can figure out power with Isquared*R!
Painandsuffering said:but the Isquared*r is a little easier with the resister in the circuit because simple ohms law can be used to find your watts instead of having to use watts law. though I know both I personally prefer Isquared*R so we are both correct because both ways will work its just personal preference.
Russlk said:I want to point out that there is a problem in having too large a resistor in series with an incandescent lamp. The lamp resistance increases with temperature which increases the power dissapated which increases the resistance which --- you see where this is going?
ljcox said:As for the resistor power calculation, it is easier, in this case, to use V * I since both are known. Why square current or voltage when you don't need to?