Calculating Electric Potential Differences

In summary, the conversation discusses the calculation of electric potential differences using the equation ΔV = -W/q. The first part of the problem is solved, but there is confusion as to why the answers for (a) and (b) are not negative. It is clarified that the negative charge of the electron should be taken into account, resulting in positive values for V(B) - V(A) and V(C) - V(A).
  • #1
G-reg
44
0

Homework Statement


When an electron moves from A to B along an electric field line in the figure below, the electric field does 2.00 10-19 J of work on it.

What are the electric potential differences:
(a) VB - VA

(b) VC - VA

(c) VC - VB


Homework Equations


Ok so I know that the equation to use in this case is that of, [tex]\Delta[/tex]V = [tex]\frac{-W}{q}[/tex]


The Attempt at a Solution


I understand how to choose the equation I've chosen and how to get the right answer. What I don't understand is why the answers to (a) and (b) aren't negative when the equation shows that they should. Can anyone help?
 
Physics news on Phys.org
  • #2
I don't have all the problem details (not enough to actually work out the problem). But allow me to speculate: Forgot the negative charge of the electron maybe? :wink: There's enough information for me to do the first part.

The given wording was "When an electron moves from A to B [...] the electric field does [positive value] J of work on it."

If the above statement applied to a test charge it means the V(A) is greater than V(B). But we're not dealing with a positive test charge. We are dealing with a negative electron :cool:. So given the negative charge, the statement implies, V(B) is greater than V(a). Therefore,

V(B) - V(A) is positive.
 
Last edited:

FAQ: Calculating Electric Potential Differences

What is electric potential difference?

Electric potential difference, also known as voltage, is the measure of the difference in electric potential energy between two points in an electric field. It is the force that causes electric charges to flow from a higher potential to a lower potential.

How do you calculate electric potential difference?

To calculate electric potential difference, you need to know the electric potential at two points and then subtract the lower potential from the higher potential. The formula is V = V2 - V1, where V is the potential difference, V2 is the potential at the second point, and V1 is the potential at the first point.

What are the units of electric potential difference?

The units of electric potential difference are volts (V), which is equivalent to joules per coulomb (J/C). This means that for every coulomb of charge, there is a certain amount of energy in volts.

How does distance affect electric potential difference?

The electric potential difference between two points is directly proportional to the distance between them. This means that as the distance increases, the potential difference decreases. This relationship is described by the inverse-square law, where the potential difference is inversely proportional to the square of the distance.

Can electric potential difference be negative?

Yes, electric potential difference can be negative. This occurs when the potential at the first point is higher than the potential at the second point. A negative potential difference is an indication that the electric charges are flowing in the opposite direction, from the lower potential to the higher potential.

Back
Top