I want to convert 0-20mA to 0-5 volt. i know for this i should use a 250 Ohm resistor. My question is what should be the power rating of the resistor?
Maximum power will be consumed at maximum voltage and current. P = VI = 5V x 20mA = 0.1W
So maximum power consumed by the resistor will be 0.1W at 20mA. A quarter-watt resistor will be sufficient for this application.