Hi, I am having a dilenma of this RC circuit, basically, R2 is the internal resi

Question

Hi, I am having a dilenma of this RC circuit, basically, R2 is the internal resistance of the voltmeter and R1 is a resistor connected in series with the capacitor. I want to find the voltage across the capacitor during CHARGING. I know that for normal series RC circuit, the voltage across the capacitor is V = V0 (1 - e-t/RC) So using voltage divider rule and the fact the resistors are connected in series I have my answer V = V0(R2 / (R1 + R2)) (1 - e-t / ((R1 + R2)C))) But apparently the answer is : V = V0(R2 / (R1 + R2)) (1 - e-((R1 + R2).t) / (R1 . R2 . C)})) It seems the total Resistance they use for ONE TIME CONSTANT is the total resistance of the two resistors in parallel, but why is it so???

Explanation / Answer

your answer is wrong because you have uesed the formula for both R1 and R2 are in series of Capicitor but that is not true, R2 is in parrallel of C.

so by parrel combination

total resistance = R2*R1/(R2+R2)

and V = Vo*R2/(R1+R2)

so last answer is correct

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