Different answer from teacher's .

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In summary, the question asks for the magnitude of the charge on each of two equal but opposite point charges, with a given electric field of 1750 N/C at the midway point between them. The student found an answer of 4.98 x 10^-9 C using the equation E=F/q, but the teacher's given answer is 6.2 x 10^-10 C. The student is unsure if their calculation is incorrect or if the teacher's answer is wrong. However, the student is reminded that the electric field at the midway point is the result of the superposition of the electric fields from both point charges, and thus the individual electric fields must be added together to find the magnitude of the charge on each point
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dncnqn
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different answer from teacher's...

Okay, here's what the question says in my book: The electric field midway between two equal but opposite point charges is 1750 N/C, and the distance between the charges is 16.0 cm. What is the magnitude of the charge on each?
I found what the force would be equal to and put it in place of F in E=F/q. When I worked it out I got 4.98 x 10^-9 C but the answer my teacher gave us was 6.2 x 10^-10 C. So am I not getting it or did he give the wrong answer? Any help would be much appreciated, thanks!
 
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  • #2
dncnqn said:
Okay, here's what the question says in my book: The electric field midway between two equal but opposite point charges is 1750 N/C, and the distance between the charges is 16.0 cm. What is the magnitude of the charge on each?
I found what the force would be equal to and put it in place of F in E=F/q. When I worked it out I got 4.98 x 10^-9 C but the answer my teacher gave us was 6.2 x 10^-10 C. So am I not getting it or did he give the wrong answer? Any help would be much appreciated, thanks!

Er... what "force" are you calculating? The force exerted on one by the other? How could you know this? All you are given is the electric field at the midway point. There's NO charge here for you to use for the "q" in F=qE. Both of the charges given combine to produce the "E". None of them can be used as a "test charge" anymore for you to use as "q". They are both the SOURCE of the electric field.

Look up (or derive) the expression of the E-field for a point charge. You have two point charges. The electric field at the midway point for your problem is the superposition from each of them. In fact, since the point is on a line between these two, and the E-field from each points in the same direction, the E-field from the individual charges ADDS.

Zz.
 
  • #3


It's possible that your teacher may have made a mistake in their calculation or used a different method to find the answer. It's always important to double check your work and make sure all the steps are correct. If you're still unsure, it's always a good idea to ask your teacher for clarification or to go over the problem again in class. Sometimes there can be multiple ways to solve a problem and it's important to understand all the different approaches. Keep up the good work and don't be afraid to ask for help when needed!
 

What should I do if my answer differs from my teacher's?

If you are confident in your answer and have valid evidence to support it, you can respectfully bring it up to your teacher and have a discussion about it. However, if your teacher has provided a different answer with solid reasoning and evidence, it is best to accept their answer and try to understand why it differs from yours.

Why do teachers sometimes give different answers?

Teachers may have different perspectives or interpretations of a topic, which can lead to varying answers. They may also have different levels of knowledge or access to information. Additionally, teachers may have different teaching styles or methods, which can result in different approaches to a question.

How can I ensure that my answer is correct?

To ensure the accuracy of your answer, it is important to thoroughly research and understand the topic. You can also seek feedback from your teacher or peers to confirm your understanding. Additionally, double-checking your sources and evidence can help validate your answer.

Is it okay to question my teacher's answer?

Yes, it is okay to respectfully question your teacher's answer if you have valid evidence or reasoning to support your own answer. However, it is important to listen to and consider your teacher's response and reasoning before disagreeing.

What should I do if I don't understand my teacher's answer?

If you don't understand your teacher's answer, you can ask for clarification or further explanation. You can also do additional research or seek help from a peer or tutor to better understand the concept. It is important to communicate your confusion and seek help in order to fully comprehend the material.

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