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Old 11-28-2002, 07:46 PM   #1
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Default Resistor question

What watt resistor will I need for a 1.7 volt, 20mA led. There are 4 of these in a series circuit off a 9 volt battery. I know that I will need a 110ohm resistor, but found out there are 3 different types of watts: 1watt, 1/2watt, and 1/4watt. Which watt resistor will I need in my situation?
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Old 11-28-2002, 08:05 PM   #2
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Power = (Current^2)*(Resistance)

So you'll only have 0.044 Watts goin through.

You want the rating to be much more than the calculated values for the components, but in this case, the 1/4W resistor is still plenty. (5.6x the calculated rating)
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Old 11-29-2002, 03:05 PM   #3
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Thank you zads!
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