# Electric Potential Difference Problem

• Noah2305
In summary, the problem involves two charges, A (-3 C) and B (+4 C), placed 2.40 m apart. Point X is 30 cm from A, and Point Y is 30 cm from B. The goal is to find the electrical potential difference going from X to Y. The equation used is V = kQ/d, and after calculating the potential at both X and Y, the difference between the two values is the final answer. This problem does not involve electrical fields, only potentials.
Noah2305

## Homework Statement

Two charges, A (-3 C) and B (+4 C), are placed 2.40 m apart. Point X is 30 cm from A, and Point Y is 30 cm from B. What is the electrical potential difference going from X to Y?

W = △Vq

## The Attempt at a Solution

Teacher gave answer as 6.9 x 10^4 V

I am not sure whether or not to use electric force or electric potential energy in this problem. I've tried both but obviously I cannot apply it appropriately to get the answer above.

Noah2305 said:
Two charges, A (-3 C) and B (+4 C), are placed 2.40 m apart. Point X is 30 cm from A, and Point Y is 30 cm from B. What is the electrical potential difference going from X to Y?
That's not enough information. You need to be able to work out how far X is from B and how far Y is from A as well. Have you stated the whole question exactly as given to you?

You do not need to consider forces or energy. It is entirely to do with electric potential (which is not the same as electrical potential energy).
Once you have all the distance information, there are just two other things you need to know:
- the formula for the potential caused by a point charge q at distance r from it
- that potentials add, i.e. the net potential at a point in space is the sum of the potentials there caused by all the charges in the system

Noah2305
Is this a 1D problem or a 2D problem? You need to draw a sketch of the locations under consideration.

If charges A and B are 2.40 m away from each other then point X is 1.8 m away from B and point Y is 1.8 m away from A.

Here's a diagram if this helps:
2.40 m
|---------------------------------|
A_____x________________y_____B
30 cm30 cmIgnore the  it is just used for spacing. Hopefully this helps.

Also:

V = kQ / d

So it seems like it is a one dimensional problem. Have you been introduced how to calculate electrical fields yet ?

Noah2305 said:
then point X is 1.8 m away from B and point Y is 1.8 m away from A.
Not according to the diagram. Try calculating those again.
Once you have distances right, use the formula you quote to find the potential that charge A creates at X and the potential that charge B creates at X.

Lazar Lakic said:
Have you been introduced how to calculate electrical fields yet ?
No need for fields here, just potentials.

So you calculate the potential at X due to both the charge at A and the charge at B. Do the same calculation at Y. You can then readily see the difference in potential between points X and Y.

Yeah my teacher wrote the wrong answer apparently. Turns out I did it correctly by calculating the total potential difference at point X and Y then to find the change in potential difference I subtracted the X value from the Y value and got the potential difference for a point to go to X to Y. Your comments were helpful though. I appreciate your input and it did help me figure out the problem.

## 1. What is electric potential difference?

Electric potential difference, also known as voltage, is the difference in electric potential energy between two points in an electric circuit. It is measured in volts (V) and is represented by the symbol ΔV.

## 2. How is electric potential difference calculated?

Electric potential difference is calculated by dividing the change in electric potential energy (ΔPE) by the charge (q) in the circuit. This can be represented by the formula ΔV = ΔPE/q.

## 3. What is the unit of measurement for electric potential difference?

The unit of measurement for electric potential difference is the volt (V). Other commonly used units include millivolts (mV) and kilovolts (kV).

## 4. How does electric potential difference affect the flow of electric current?

Electric potential difference is what drives the flow of electric current in a circuit. The greater the potential difference, the greater the force pushing the electrons through the circuit. This is known as the "pressure" or "voltage" of the circuit.

## 5. What factors can affect the electric potential difference in a circuit?

The electric potential difference in a circuit can be affected by a number of factors, including the type of power source used, the resistance of the circuit, and the distance between the two points in the circuit. Changes in any of these factors can alter the electric potential difference and impact the flow of electric current.

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