Ground and Other References: Video Lecture Q

studiot

Joined Nov 9, 2007
4,998
Now can you take this information and apply it to your circuit?

You need to realise that connecting two or more points of the circuit to 'earth' will cause them to have the same potential (be at the same voltage) regardless of the currents flowing and regardless of the resistance between those two points, in the circuit or within the earth.

So you need to set up voltage equations based on this fact and for instance Kirchoffs laws.

Then use current equations if you require more.
 

Thread Starter

foolios

Joined Feb 4, 2009
163
am I right in saying that he is only denoting ground in his circuit example at time 2:42 as the negative side of the circuit?
http://www.allaboutcircuits.com/videos/55.html
He isn't really putting a ground there, it's just his way of showing what side of his circuit is negative and positive, right?

"You need to realise that connecting two or more points of the circuit to 'earth' will cause them to have the same potential (be at the same voltage) regardless of the currents flowing and regardless of the resistance between those two points, in the circuit or within the earth."

Dangit...
Why would we have two grounds to earth?

If you mean in general, I guess, ya; I would think that any number of connections to a ground would equal each other in potential. They are all at zero in respect to each other. As long as we're talking about one complete circuit that they are all sharing.

This the answer?
 

shortbus

Joined Sep 30, 2009
10,045
Foolios, The last two sentences in the text in the drawing you posted should be reread by you.

The left drawing is just showing what is "IMPLIED" in the right drawing.

you probably got the drawing from something about schematics, correct?
This is just showing how you don't have to clutter up the schematic with all the connecting line to ground.

they do the same thing with supply voltages on schematics.
 

Thread Starter

foolios

Joined Feb 4, 2009
163
When you see the ground nodes on the way bottom of each wire that means those wires connect to ground. So on the circuit to the right they would both connect together.

I think now I realize you were just trying to say what the professor was saying in the video during the post I made above.
That the grounding symbol in the left circuit just means that that side is tied into the negative terminal. It's just letting you know that that's the negative side of the circuit.
 

Thread Starter

foolios

Joined Feb 4, 2009
163
"This is just showing how you don't have to clutter up the schematic with all the connecting line to ground.

they do the same thing with supply voltages on schematics. "


Ok, this is tending towards how the same word is being used for two meanings like the ac wording was confusing. When I talked about how returns were being called grounds.

So, the simple answer is that the schematic is showing that the negative side of the circuit IS ground. Or in kinda like ac words, the return/ground...
 

Thread Starter

foolios

Joined Feb 4, 2009
163
Here is an AC circuit with multiple grounds.


This is borrowed from the videos on here. It's in the section about power supplies.

Now if that circuit, well, lets pretend there aren't diodes there just resistors or loads; if it didn't have the grounds, would it work? I mean, would current travel around the circuit if there weren't any grounds attached to it?

Sorry for beating this topic up, but I am trying to find as many semblances of what wer're talking about to make it clearer. I have seen three phase transformer schematics that kind of resemble this and it was confusing as to why there are grounds center tapped onto the buckets. The ones you see on the power poles.

EDIT: Well, ok, we can't use loads for my question because now that I think about it, loads will usually have grounds on them. I think motors have grounds built in. So lets just say those are resistors.
 

thatoneguy

Joined Feb 19, 2009
6,359
In that pic, those two points are connected.

The center tap of the transformer is considered ground, and the resistor is connected to that same point/wire.
 

Thread Starter

foolios

Joined Feb 4, 2009
163
oh yeaahhhhhh, got yas.

And nothing's going to happen in this circuit until something, like a motor starts to draw power or is there a constant power being applied to this circuit with or without draw?
 

t_n_k

Joined Mar 6, 2009
5,455
Here's another perspective in the attachment - for what it's worth. I'm currently playing around with a data acquisition unit which has options for either a floating source or ground referenced source.
 

Attachments

Top