runny4
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#1
Report Thread starter 5 years ago
#1
For the paper below, in question 17biv, i don't understand why you can't use the average potential difference from 17bi instead of 2V. Please help

http://qualifications.pearson.com/co...-June-2014.pdf
- Paper

http://qualifications.pearson.com/co...-June-2014.pdf
- Mark Scheme

http://qualifications.pearson.com/co...-June-2014.pdf
- Examiner's report
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The-Spartan
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#2
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The equation

C=\frac{Q}{V} is used for the charge or discharge of a capacitor and is therefore usually written

C=\frac{Q}{\Delta V}.

In the one charge/discharge cycle, the change in voltage is not equal to the average voltage. Thats why you cant use it.

As the question asks for the charge when there is one discharge of the capacitor, you have to look at the max voltage - min voltage, which will be 6.2-4.2 which is 2V.
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runny4
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#3
Report Thread starter 5 years ago
#3
(Original post by The-Spartan)
The equation

C=\frac{Q}{V} is used for the charge or discharge of a capacitor and is therefore usually written

C=\frac{Q}{\Delta V}.

In the one charge/discharge cycle, the change in voltage is not equal to the average voltage. Thats why you cant use it.

As the question asks for the charge when there is one discharge of the capacitor, you have to look at the max voltage - min voltage, which will be 6.2-4.2 which is 2V.
OK Thank you
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