Potential Difference: Definition & Calculation

[Science Proff]

Hey every one, can you please tell me what potential difference is. Is it the amount of work needed to bring one coulomb charge from a point to another or is it the amount of work done to bring one coulomb charge from a point to another.

 

[quantum123]

"Needed". Whether the act is done or not does not matter. That is why it is called "potential" difference.

 

[Science Proff]

"Needed". Whether the act is done or not does not matter. That is why it is called "potential" difference.

Hey but then in either ways, the charge that will be carried will be of 1 coulomb right, then how can it be that for only one coulomb charge, there will be different amounts of energy needed to carry it? (since it is constant) I mean on what basis does the energy needed to take one coulomb charge from one point to another is specified. Isn't it that for one coulomb charge everywhere, the energy required is same?

 

[quantum123]

Let me ask you a question:
Will carrying 1kg stone 1 storey upstairs or 2 storeys upstairs require the same energy?

 

[Science Proff]

Of course, I mean, the minimum energy required would be same. It only depends on you later how much energy would you apply. The thing is, the minimum energy required is same.

 

[Science Proff]

Hey please answer

 

[quantum123]

Let me put it into a problem format:

Person A lifts 1 kg stone from sea level to a height of 10m. How much work has he done?
Person B lifts 1 kg stone from sea level to a height of 20m. How much work has he done?

Person A moves a charge of +1C 0.01m from the -ve plate toward +ve plate of a capacitor with uniform field strength of 1V/m. How much work has he done?
Person B moves a charge of +1C 0.02m from the -ve plate toward +ve plate of a capacitor with uniform field strength of 1V/m. How much work has he done?

 

[Science Proff]

So are you saying that to take the 1 coulomb charge, the energy required depends on the displacement of the charge? (Distance traveled)

 

[cshum00]

It is not the amount of work needed to move a coulomb charge but how likely it will move a coulomb charge and with how much energy when it reaches the other end. I might be wrong but i believe that Electrical Potential Difference borrows the concept of Gravitational Potential Difference.

Imagine the this, you have 2 rocks with the same mass. One is displaced 5m above ground and another one 10m above ground.
-Which one is more likely to fall down?
Both are going to fall down since the potential difference is not zero.
-Which one will have more energy when it reaches the ground?
The one with higher potential or being at 10m will have more energy when it hits the ground.
-What if there is a table in between the floor and the ground with 5m of height?
If there is a table at 5m, it will become the new ground for the potential difference. Meaning that the rock at 10m will only fall 5m and have less potential energy when it reaches the table. And the rock at 5m will not fall because it is already at the table making it with 0 potential difference.

Now do you get why it is called potential difference? The same concept can be applied to electricity except that the attraction are not done by mass but the charges. And the other thing is that Electrical Potential Difference not only provide the force for pull but also for push.