# Ground in electric circuits

1. Nov 21, 2013

### aaaa202

The term ground has always confused me. For instance: I have always thought of a battery as a collection of negative charges at the -pole and positive charges at the +pole. But with this picture what does it mean that one pole is grounded. To be grounded is I guess ideally to be connected to the whole universe. So any charge you had on the pole will effectively spread out to the entire earth leaving no charge at the pole. Am I right so far?
Well then in this case what happens to the voltage gap across the battery poles? In the first case it was established because you had to take away electrons from the positive pole and bring them up to negative pole fighting the electric field in both cases. But in the case of a grounded pole, you no longer have to fight the negative charges (or positive depending on which pole is grounded). So doesn't grounding alter the voltage difference?

2. Nov 21, 2013

### davenn

hi aaaa202

there's a lot of variation used with the term Ground (GND)
you can have an Earth ground where there is a physical connection to GND
the negative rail on a circuit can and will often be called GND, 0V or negative
You can have a chassis ground where the GND of the mains power cord and possibly the 0V rail of the circuit are connected to the metal chassis of the equipment
You can also in analog/digital circuits have separate analog and digital ground rails ( tracks on a PCB)

its becomes important to correctly differentiate these where you may have a multiple rail power supply/system

say a power supply that has +15V, a 0V and a -15V rails ....
That 0V rail may also be called GND and may or may not be connected to the Earth GND and metal chassis

hope that helps and doesn't confuse you more

cheers
Dave

3. Nov 23, 2013

### CWatters

The distribution of charge across a conductor like the earth isn't and doesn't have to be uniform (think about lightning). Opposite charges also attract.