What is the role of a grounded point in a circuit?

In summary: I think I've got it now. My confusion was stemming from a misunderstanding of what it means to have a...ground.
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  • #2
AbhinavJ said:

Homework Statement



https://docs.google.com/file/d/0B0FIIKckKOcKM1FmXzJkYWJiZ2c/edit?usp=docslist_api

Homework Equations

The Attempt at a Solution


Shouldn't the potential be 10 as it is directly connected to the battery?
Potential is assumed w.r.t some reference called 'ground' which is assumed to be at 0V. In your circuit, point x is at 0V and not the -ve terminal of the battery. So, if you say A is at 10V, that means -ve terminal of the battery is earthed (which is not). So, taking x as reference, A is at 7.5 V and the potential distribution from A to B is not 10V to 0V ..its actually 7.5V to -2.5V..
 
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  • #3
cnh1995 said:
Potential is assumed w.r.t some reference called 'ground' which is assumed to be at 0V. In your circuit, point x is at 0V and not the -ve terminal of the battery. So, if you say A is at 10V, that means -ve terminal of the battery is earthed (which is not). So, taking x as reference, A is at 7.5 V and the potential distribution from A to B is not 10V to 0V ..its actually 7.5V to -2.5V..

Can you please tell me how to calculate that? Even a hint would do. Thanks
 
  • #4
member has been warned that providing complete or almost complete solutions is forbidden at Physics Forums
AbhinavJ said:
Can you please tell me how to calculate that? Even a hint would do. Thanks

[ mentor note: content deleted ]
 
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  • #5
cnh1995 said:
PD between A and B is 10V and voltage across each capacitor will be 2.5V (equal). So, between X and A, there are 3 capacitors. So, VAX is 7.5V with x at 0V potential. This means, A is at 7.5V.

Why is placing the ground between the third and fourth capacitor any different than simply removing the fourth capacitor and unearthing the point X?
 
  • #6
Kinta said:
Why is placing the ground between the third and fourth capacitor any different than simply removing the fourth capacitor and unearthing the point X?
@Kinta :

Is this a question to help the OP, or are you asking this because you don't know the answer?

IMG_20150604_140746.jpg
 
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  • #7
SammyS said:
@Kinta :

Is this a question to help the OP, or are you asking this because you don't know the answer?

I'm asking because I don't know. I should know, but I don't. I figured if I had difficulty understanding this concept, someone else (maybe even OP) might have similar troubles.
 
  • #8
SammyS said:
Please read the rules for offering homework help.

Do NOT give complete solutions.
My apologies..
 
  • #9
Kinta said:
Why is placing the ground between the third and fourth capacitor any different than simply removing the fourth capacitor and unearthing the point X?
I think it will depend on where you assume the ground (0V) after X is unearthed. But I'm not getting your idea of removing the fourth capacitor..
 
  • #10
Kinta said:
Why is placing the ground between the third and fourth capacitor any different than simply removing the fourth capacitor and unearthing the point X?
If you simply remove the fourth capacitor, then the 10 Volt potential difference is split across only three capacitors instead of four.
 
  • #11
SammyS said:
If you simply remove the fourth capacitor, then the 10 Volt potential difference is split across only three capacitors instead of four.

I understand that. What I don't understand is if this is any different than placing the ground at the point X in OP's picture.
 
  • #12
Kinta said:
I understand that. What I don't understand is if this is any different than placing the ground at the point X in OP's picture.
If you remove the 4th capacitor, automatically point x (ground) will be connected to the -ve terminal of the battery. So, A will now be at 10V instead of 7.5V..
 
  • #13
Once the ground is placed at point X, why does it matter that there is a capacitor between it and the -ve terminal? Aren't they both grounded?
 
  • #14
Kinta said:
Once the ground is placed at point X, why does it matter that there is a capacitor between it and the -ve terminal? Aren't they both grounded?
No they aren't..Ground is just a reference point..It can be anywhere in the circuit.. Battery neither knows nor cares where you place the ground. It will just establish a 10V pd between A and B. How to "see" the 10V path is decided by the ground. If ground is at B, then it will be
10V(point A)---7.5V---5V---2.5V(point X)---0V(point B). In the problem, X is assumed to be 0V. So, the 10V path is
7.5V(A)-5V-2.5V-0V(X)- -2.5V(B)..
 
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  • #15
cnh1995 said:
No they aren't..Ground is just a reference point..It can be anywhere in the circuit.. Battery neither knows nor cares where you place the ground. It will just establish a 10V pd between A and B. How to "see" the 10V path is decided by the ground. If ground is at B, then it will be
10V(point A)---7.5V---5V---2.5V(point X)---0V(point B). In the problem, X is assumed to be 0V. So, the 10V path is
7.5V(A)-5V-2.5V-0V(X)- -2.5V(B)..

Ok. I think I've got it now. My confusion was stemming from a misunderstanding of what it means to have a grounded point in a circuit. Thanks. :biggrin:
 
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Related to What is the role of a grounded point in a circuit?

1. What is potential at a point in a circuit?

The potential at a point in a circuit refers to the electrical potential or voltage at that specific point. It is a measure of the amount of electric energy that a charged particle would possess if placed at that point.

2. How is potential at a point in a circuit measured?

The potential at a point in a circuit is measured using a voltmeter. It is connected in parallel to the component or point where the potential is to be measured, and the reading on the voltmeter is the potential at that point.

3. Does potential at a point in a circuit affect current flow?

Yes, the potential at a point in a circuit affects the current flow. According to Ohm's law, the current flowing through a circuit is directly proportional to the potential difference or voltage applied. This means that a higher potential at a point will result in a higher current flow through that point.

4. How is potential at a point in a circuit related to energy?

Potential at a point in a circuit is directly related to energy. It is a measure of the electric potential energy per unit charge at that point. A higher potential at a point means that more energy is needed to move a charged particle to that point, while a lower potential means less energy is required.

5. Can potential at a point in a circuit be negative?

Yes, potential at a point in a circuit can be negative. This happens when the potential at that point is lower than the reference point or the ground. It indicates that the electric field is directed towards that point, and a charged particle would have a decrease in potential energy if moved towards that point.

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