I was working through the following problem: The negative termincal of a 12V car battery is connected to the car frame which can be regarded as 'ground', at a potential of 0V. What is the potential of the other terminal? The answer is +12V, but I cannot understand why. Could someone give me an explanation to this? Also, what does it mean that the car frame can be regarded as 'ground'? Any help would be greatly appreciated, I'm so lost!