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[on:]

I just obtained an Arduino Uno and was trying to work through some of the tutorials to become more familiar in using it.

However, I ran into a problem in that I went to go buy some of the components, and the folks at the electronics store wanted to know the wattage. For example, Blink ( http://arduino.cc/en/Tutorial/Blink ) requires a 220 ohm resistor, but the store sells 1/2 watt 220 ohm resistors, 1/4 watt 220 ohm resistors, and so on.

So how do I determine the needed wattage for the resistors, potentiometers, et cetera?

Thank You

[Reply #1 on:]

First to answer your question - you calculate it from the voltage across the resistor - P = V*V/R where P is in watts, V is in volts, R is in ohms or P = I * I * R where I is in amperes and R is in ohms.

Now having said that the currents in the tutorial you are working with are so small that  any of the resistors you found  (1/2 W, 1/4 W even 1/8 W) will work just fine.