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MrToodles4

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Just a quick question 5b I don't understand:
http://pmt.physicsandmathstutor.com/...s%201%20QP.pdf

It says to find the volt across the 150 microfarad capacitor; so I did 150/600 * 6V to get 1.5V however, the markscheme says its wrong and it should be 4.5V??? Can someone please explain - many thanks

MS: http://pmt.physicsandmathstutor.com/...s%201%20MS.pdf

Somebody1234

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Well as the MS says charge is constant is a series circuit (because current is constant) so if C=Q/V then capacitance is inversely proportional to voltage so lower capacitance=higher share of voltage

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MrToodles4

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(Original post by Somebody1234)
Well as the MS says charge is constant is a series circuit (because current is constant) so if C=Q/V then capacitance is inversely proportional to voltage so lower capacitance=higher share of voltage

Many thanks for the reply - so is this ALWAYS the case in a series circuit with a capacitor???

Somebody1234

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(Original post by MrToodles4)
Many thanks for the reply - so is this ALWAYS the case in a series circuit with a capacitor???

I suppose so, tbh idk what exam board u do but ive never seen an edexcel question with 2 capacitors in series

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MrToodles4

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(Original post by Somebody1234)
I suppose so, tbh idk what exam board u do but ive never seen an edexcel question with 2 capacitors in series

So what calculation would you use for this then? Cause mine gives the answers in the wrong way around. Its OCR A.

Somebody1234

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(Original post by MrToodles4)
So what calculation would you use for this then? Cause mine gives the answers in the wrong way around. Its OCR A.

Its all about ratios u cant really think of it as a single calculation thatll get u to the answer

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MrToodles4

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(Original post by Somebody1234)
Its all about ratios u cant really think of it as a single calculation thatll get u to the answer

Alright so basically I just need to remember to swap them, so that 1.5V i worked out would be for the high capacitance capacitor

Somebody1234

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(Original post by MrToodles4)
Alright so basically I just need to remember to swap them, so hat 1.5V i worked out would be for the high capacitance capacitor

Ok well if uve got 2 capacitors in series u can literally do V=EMF*(Total capacitance - capacitance)/Total capacitance but that equation stops working if u have more than 2, but as u said up there that way of thinking works fine

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