# What does it mean for an object to act as the "ground"?

• ellieee
In summary, when we say we ground all other conductors, we mean we connect them to a voltage source of zero volts.

#### ellieee

Homework Statement
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Relevant Equations
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they said that Y is acting as the ground, what does it mean?

It means that Can Y supplies (some of ) its free electrons so that Can X can have negative charge.

But it is some sort of overstatement, because a vital characteristic in order for something to be called ground is not only to be able to give free electrons but also to keep its potential constant regardless of how many electrons it gives or takes. And this thing (constant potential) does not hold for Can Y.

rude man
Watch this:

Can Y is not the ground in the second frame (nor the first, for that matter. I guess you can only go so far with comic books.)

There are two hands in the second frame ; how many people do you think that is ?

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hmmm27 said:
Can Y is not the ground in the second frame (nor the first, for that matter. I guess you can only go so far with comic books.
Indeed. It is sloppily worded.

ellieee said:
Homework Statement:: nil
Relevant Equations:: nil

View attachment 286882
they said that Y is acting as the ground, what does it mean?
I think it means you don't have the best physics instructor. That wording is confusing, at best, but I'd say it's just wrong. Perhaps they should have just said "can Y is a source of the excess electrons in can X".

Doc Al said:
Watch this:

that's the video I was watching..

When we say we ground all other conductors, we mean that we connect them to a voltage source of zero volts. Recall that voltage is always defined relative to a reference. For instance, we may take one of the conductors as the ground reference and then measure all absolute voltages relative to this conductor.

We may connect the conductors to a much larger body, one with infinite capacitance. Then charge can be freely removed or added to the ground without changing its potential. In other words, it can be a direct physical connection to the earth.

Delta2