Electrical Potential, Voltage, Work

[chembloke]

Hi guys,

So my question is related to Electical Potential Eenrgy and Voltage. First off, I am using the Physics book by Cutnell, 8th Edition. If anyone would like to turn to the page I am on, it is page 570 or around there if you have the newer edition.

So, they first relate Work by equation 19.2 as shown below, and then Voltage by equation 19.3. So i get that part, sorta.

But when it comes to Voltage, as shown in equation 19.4, is Voltage (negative) Work divided by charge?

in equation 19.2, they use EPEA-EPEB, but why not the other way around.
Then 19.4 calcualtes Voltage by using EPEB-EPEA, but Work is now negative.

So i guess my main question -- in 19.2, why is EPE calculated as the first point minus the second point, and not the other way around?
The other question relates to Voltage and negative work? I've read the section twice now and it is still not sticking.

Sorry if my question is complicated, I'll try to answer any questions you have about my question. :tongue:

Thank you!

 

[Drakkith]

You should probably type out the equations. Most people do not have your textbook.

 

[chembloke]

Not sure if the equations are showing in the original post, but here they are in case they are not showing up.

 

[rcgldr]

Is Voltage (negative) Work divided by charge?

Voltage is the potential energy divided by charge. The change in voltage is related to work divided by charge.

 

[sardar]

Hi there,

Electrical potential energy is the potential energy that a charged particle possesses due to its position in an electric field. This energy can be converted into kinetic energy when the particle moves. The work done by an external force on the charged particle to move it from one point to another is equal to the change in its electrical potential energy. This is shown in equation 19.2.

Voltage, on the other hand, is the measure of the potential difference between two points in an electric field. It is calculated by dividing the work done by the charge of the particle. This is shown in equation 19.3.

In equation 19.4, the negative sign represents the direction of the electric field. When calculating the voltage, the work done is always in the direction opposite to the electric field, hence the negative sign. This is also why the order of the points is reversed in equation 19.4 compared to 19.2.

As for your question about why EPE is calculated as the first point minus the second point, it is simply a convention. It doesn't matter which point is chosen as the reference, as long as it is consistent throughout the calculation.

I hope this helps clarify your questions. Keep up the good work in your studies!