In my opinion, "grounded" means having the same potential as the potential at infinity, which is usually set to zero. Now if we consider a conductor inside a uniform electric field, what is the meaning of a conductor being "grounded"?
$\begingroup$
$\endgroup$
2
-
1$\begingroup$ This might actually be better on Electrical Engineering. Which is not to say that it is off-topic on Physics, but you'll encounter more people intimately familiar with all the myriad the "real world" uses of the term over there. $\endgroup$– dmckee --- ex-moderator kittenCommented Jun 4, 2014 at 16:01
-
$\begingroup$ @user139981: Don't forget to accept an answer once one of them is acceptable to you. $\endgroup$– DanielSankCommented Jun 8, 2014 at 17:16
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
3
In common usage "grounded" means
Connected to a conductor which I have arbitrarily deemed to be at an electric potential of 0, and which has such high capacitance that you can assume it never builds up any charge.
Of course, the word comes from the convention that we literally use the ground as a potential reference. In any experimental physics building there's a huge spike of metal that's literally driven into the ground. That spike is big and fat so that it's resistance is really low. By connecting one of the wires of each piece of equipment to this spike you are guaranteed that they are all using the same voltage as their reference.
This is important because current flows through that "ground wire." If the resistance is not small then there will be a voltage difference between different points on the ground reference, which means that different pieces of equipment each measuring the same voltage would report different numbers.
There are other considerations, but that's the essence.
answered Jun 4, 2014 at 20:25
-
$\begingroup$ The ground reference to which things are connected is assumed to have zero resistance $\endgroup$– user56903Commented Jul 8, 2015 at 9:32
-
$\begingroup$ @DirkBruere Only if you're not doing any work at high frequency. At high frequency the resistance and inductance of grounds are absolutely never just "assumed" to be zero ;-) $\endgroup$ Commented Jul 8, 2015 at 17:26
-
$\begingroup$ Yes, but for the purposes of discussing "the ideal ground" it is true. Real life is different $\endgroup$– user56903Commented Jul 8, 2015 at 18:50
$\begingroup$
$\endgroup$
2
in my opinion, and based on convention, grounded means the system won't build up any potential.
Say you have one end of battery connected to a sphere - not grounded, and sphere builds up a potential difference relative to the other terminal. Now, while the system intact, you connect the sphere to the other terminal of the battery - grounded, the sphere won't build up potential difference now.
So, in your question, I believe the conductor is connected to a ground supply.
-
$\begingroup$ I'd agree with this. A conductor connected to "the ground" has access to a very large reservoir of charge, so that charges may move on or off the grounded conductor without changing its potential. The name arises because we have such a large reservoir underfoot. $\endgroup$– rob ♦Commented Jun 4, 2014 at 20:11
-
$\begingroup$ I never quite thought of it in terms of charge accumulation. Good answer. $\endgroup$ Commented Jun 4, 2014 at 20:35