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What I don't understand is why the the two voltage sources are subtracted when working out the emf for part a, The graph does not show the orientation of the solar panel so I thought I was to assume they had the same orientation?

for part b why is it that when working out the voltage across V1 and V2 for V1 you subtract the voltage dropped across the internal resistance while for V2 you add? Thank you.

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  • $\begingroup$ I assume you mean part a.i and part a.ii, as you haven't posted part b. $\endgroup$
    – Brionius
    Oct 24 '14 at 19:19
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Part a.i:

It would be a clearer question if it specified the orientation of the solar panel, but since it states the battery is being charged, it makes sense to assume the solar panel is oriented in such a way that the current is flowing into the positive terminal of the battery (the opposite way from the way it would be flowing if the battery were discharging). So the positive side of the solar panel is facing the positive side of the battery.

Part a.ii:

The reason is that the current is flowing in opposite directions through those two resistors; from top to bottom through the battery's internal resistance, and from bottom to top through the solar panel's internal resistance. Thus the voltage across those resistors have opposite signs as measured by the voltmeters.

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  • $\begingroup$ Thank you for part ai,If I understood correctly does this mean the voltage across the cell is negative while the voltage across the 24.6 is positive. Furthermore for part aii when working out V2 should it not be -12.6-(-5.7*0.1)=-12.03 V? $\endgroup$ Oct 25 '14 at 14:21

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