Ok just for you search people I did a search and I found lots of stuff but I did not find the specific answer to my specific question. I have a red wire and a black wire on my computer fan , the man at the 2nd hand computer place said the black wire was the ground wire , ?? my question is on my cell phone charger there is a smooth wire and a wire that has a grove along the side , what one do I wire the black wire to ???? Thank you.