Is the Energy Stored in a Capacitor Really QV Instead of QV/2?

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Homework Help Overview

The discussion revolves around the energy stored in a capacitor and the potential discrepancy between the formulas QV and QV/2. Participants are examining the implications of these formulas in the context of energy calculations related to capacitors.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are exploring the correctness of the energy values calculated, specifically questioning whether the energy supplied by the voltage source is being interpreted correctly. There is also discussion about the potential confusion between the two energy formulas.

Discussion Status

Some participants have confirmed the calculated energy value of 0.288mJ, while others are questioning the interpretation of the energy supplied by the voltage source. There is an ongoing exploration of whether the model answer may have been misprinted, with no explicit consensus reached yet.

Contextual Notes

Participants are considering the possibility of a mistake in the answer key and are discussing the assumptions underlying the energy calculations. There is an acknowledgment that mathematical support for the claims could be provided, but it may not be necessary for this problem.

Clara Chung
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Homework Statement
Attached below. I want to check whether my answer is right because the model answer is 0.576 mJ. Thank you.
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0.288 millijoules looks right.
 
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Yes, 0.288mJ looks correct.
But the energy supplied by the voltage source is 0.576mJ, and maybe that's what they printed as the model answer by mistake.
 
cnh1995 said:
Yes, 0.288mJ looks correct.
But the energy supplied by the voltage source is 0.576mJ, and maybe that's what they printed as the model answer by mistake.
cnh1995: I agree that 0.288mJ looks correct. But I have not been able to see how to support your statement that "the energy supplied by the voltage source is 0.576mJ". Assuming you are correct, is it possible to interpret the assigned calculation to mean the energy supplied by the voltage source?
 
Last edited:
sojsail said:
But I have not been able to see how to support your statement that "the energy supplied by the voltage source is 0.576mJ".
Well, it can be shown mathematically, but I don't think this problem requires that. :smile:
I mentioned it because I thought perhaps the given wrong answer key had something to do with it.
 
Maybe they mistakenly took the energy to be QV instead of QV/2?
 
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