An electron is placed at Point P, Calculate the Potential Energy

In summary, the conversation discusses the method for calculating the electric potential energy of an electron at a given point, using the values for net force, net electric field, and electric potential provided in the problem statement. It clarifies that the potential energy at a point is the work done in moving the electron from infinity to that point, and provides the correct calculation for the potential energy.
  • #1
aaika
4
0
Homework Statement
An electron is placed at point P.
Calculate the electric potential energy of the electron in units of Joules
Relevant Equations
Net Force = 200.97N
Net Electric Field = 2.51e6N/C
Electric Potential at point P = 5.43e6V

Ub-Ua = -qEd
Change in U = -qEd if F is parallel to d
243768

Not quite sure how to approach this question - do I need to calculate -qEd for all three charges and then the electron and add them together?
Thanks
 
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  • #2
Hi @aaika,

Welcome to Physics Forums!

You're relevant equations look more like given data that would belong in the problem statement.

The Net Force looks suspiciously large. 200 N applied to an electron by an electric field would imply an amazingly large electric field, much larger than what you've specified as the net electric field.

Are you certain that the problem statement is complete and presented exactly as you received it?
 
  • #3
gneill said:
Hi @aaika,

Welcome to Physics Forums!

You're relevant equations look more like given data that would belong in the problem statement.

The Net Force looks suspiciously large. 200 N applied to an electron by an electric field would imply an amazingly large electric field, much larger than what you've specified as the net electric field.

Are you certain that the problem statement is complete and presented exactly as you received it?

Thank you :)
Absolutely certain. The three numbers I provided are the correct answers for the previous questions leading to this one. I have directly copy + pasted the problem so there is no missing information.
 
  • #4
But if we take your net electric field value, 2.51e 6N/C, and insert the charge of an electron in the equation ##F = qE##, we arrive at a force value of only about ##4.0 \times 10^{-13} \text{N}##. This contradicts your net force value by a rather large margin. Is the force force value you've given really the force on the electron?
 
  • #5
243772
243771


Attached are screenshots of the answers being marked as correct.
 
  • #6
Your original problem statement did not indicate that the given values for Net Force and Net Electric Field pertained to other bodies than the electron. How were we to guess? You should always provide the complete problem statement as given.
 
  • #7
You have the electric potential at point P. It's units are Volts, which is not a fundamental unit. It is synthesized from Joules/Coulomb (##Volt = \frac{Joule}{Coulomb}##). How do you think you might arrive at the electric potential energy of the electron located at that point?
 
  • #8
aaika said:
Problem Statement: An electron is placed at point P.
Calculate the electric potential energy of the electron in units of Joules
Relevant Equations: Net Force = 200.97N
Net Electric Field = 2.51e6N/C
Electric Potential at point P = 5.43e6V

Ub-Ua = -qEd
Change in U = -qEd if F is parallel to d

View attachment 243768
Not quite sure how to approach this question - do I need to calculate -qEd for all three charges and then the electron and add them together?
Thanks

The potential energy at any point in space is the product of the "test charge" and the value of the potential at that location, i.e.

U = qV

based on the situation where V at r→∞ is zero.

For the situation where you only have 3 charges as the source charges of the potential field, then the potential potential energy at point P is the work done in moving the electron from very far away (∞) to the point P, i.e. ΔU = U(at p) - U(∞) = U(at p).

Since q = -e and V is given in your problem, this should be straightforward. But you have to have a conceptual understanding of what I described above, because this question can come in a million different varieties.

Zz.
 
  • #9
gneill said:
Your original problem statement did not indicate that the given values for Net Force and Net Electric Field pertained to other bodies than the electron. How were we to guess? You should always provide the complete problem statement as given.

My bad - I thought I included that it was relevant to Q3 when I pasted it.

ZapperZ said:
The potential energy at any point in space is the product of the "test charge" and the value of the potential at that location, i.e.

U = qV

based on the situation where V at r→∞ is zero.

For the situation where you only have 3 charges as the source charges of the potential field, then the potential potential energy at point P is the work done in moving the electron from very far away (∞) to the point P, i.e. ΔU = U(at p) - U(∞) = U(at p).

Since q = -e and V is given in your problem, this should be straightforward. But you have to have a conceptual understanding of what I described above, because this question can come in a million different varieties.

Zz.

Thank you for clarifying! I was caught up in the fact that I had Q1-3 as well as an electron and didn't know whether or not those three Q's would be influential in the formulae to figure it out.

U=qV= (-1.60e-19)(5.43e6) = -8.69e-13J which was correct.
 

1. What is an electron?

An electron is a subatomic particle that carries a negative electrical charge. It is one of the fundamental particles that make up an atom.

2. What is Point P in this scenario?

Point P refers to a specific location in space where the electron is placed. It could be a point on a coordinate plane or in an electric field.

3. How is potential energy related to an electron?

Potential energy is a measure of the energy that an object has due to its position or configuration. In this scenario, the potential energy is related to the electron's position at Point P and the electric field surrounding it.

4. How is potential energy calculated for an electron at Point P?

The potential energy of an electron at Point P is calculated by multiplying the charge of the electron by the electric potential at Point P. The electric potential is determined by the distance between Point P and the source of the electric field, as well as the strength of the field.

5. Why is calculating potential energy important in this scenario?

Calculating potential energy allows us to understand the behavior of an electron in an electric field. It helps us determine how the electron will move and interact with other particles in the system. This information is crucial in many fields of science, including physics, chemistry, and engineering.

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