I'm new to electronics and I have a question about how hot resistors get. I'm turning an old computer power supply into a workbench supply. It would run for a few seconds then turn off. I read that some power supplies won't turn on or stay on if it doesn't sense a load and to remedy this install a resistor between the +5 volt line and ground.So I soldered in a 47 ohm 2 watt resistor between +5 volt and ground and it worked, the power supply stayed on. However, after just 1 minute, I touched the resistor to check how warm it was and quickly let go. It was too hot to touch! By my calculations, the power should have been just over 1/2 watt (0.532). Should a 2 watt resistor get that hot with just a 1/2 watt load? Or have I made a mistake in my calculation?
I used V / R = I, I x V = P
I used V / R = I, I x V = P