# Potential of terminals of battery

1. Nov 30, 2015

### gracy

No it is not a homework problem I made it myself in order to clearly explain what I am trying to ask.The question could be invalid and silly therefore .If there is a 9V battery What is the potential of it's positive and negative terminals respectively?

If positive terminal's potential is 3V and potential of negative terminal -6V then there would be potential difference of 9V. Similarly if positive terminal's potential is 2V and potential of negative terminal -7v then there would be potential difference of 9V. So many answers are possible therefore potential of one terminal should be given.
Am I making sense?Or all of these are wrong?

2. Nov 30, 2015

### jbriggs444

Only potential differences are physically meaningful. Given a battery with a potential difference of 9 V between the two terminals, there is not enough information to tell you the potential of either positive or negative terminal relative to some unspecified reference.

For instance, you could ground the positive terminal. The negative terminal would then be at -9 V relative to the ground. Or you could ground the negative terminal. The positive terminal would then be at +9 V relative to the ground. Or, as you suggest, you could arrange for the two terminals to be at +3 V and -6 V. That would be perfectly reasonable.

3. Dec 1, 2015

### CWatters

You are basically correct.

However ask yourself 3V relative to what ?... and do you really need to know the voltage relative to that? My phone works just fine even when my hand is charged to several thousand volts by static electricity. Sometimes it does matter. Can you think of a situation?