But, static can damage chips and such. A typical processor runs off of 5v. Current is measured in amps, but most amateur robotics applications will typically use miliamps, one-hundredth of an amp, for a measurement. This simply means that it can supply 250 mA for 2 hours, or 125 mA for 4 hours. However, because of efficiency problems, it most likely wouldn't be able to give a full 500mA for one hour.
Resistors function like sponges in the water pipes i.e. they restrict the flow of electrons.
So, if you've got an LED powered from a 5v supply and you want to give it 20 ma, you need to find out what value resistor to use. Therefore you use a 250 ohm resistor. Many times you won't find the exact resitor value. It is ok, in most circumstance, to find the closest value. All rights reserved.