My arduino starter kit came with 20 560ohm resistors. Everytime I hook an LED up to 5V power I'm supposed to use a 560ohm resistor otherwise I might over power the LED and burn it out.
Check with my multimeter I see 5.04v before the resistor and, 1.98v after the resistor. The resistor is dropping the voltage as it should. My question is the math, how does one calculate what resistor to use for a given situation. What if I want 3v out instead of 2v?
Ohm's law saws that the resistance is V * I = R. V in this case would be 3v, but how do I know what I is?