a resistor (of unknown constant resistance) and a 0.02 farad capacitor are connected to a series with an emf of E = 100 volts. the initial charge of the capacitor is 5 coulombs. if at t=1/10 second the current flowing is 30/e amperes on the reverse direction, find the value of the resistance

Question

anonymous · Answer

For capacitor Q=CV where Q is charge on it , C is its capacitance and V is voltage across it. So voltage across a capacitor of 0.02 farad with charge 5 C, is 5 / 0.02= 250 Volts. Since resistor and capacitor are in series, thus there are two voltages across resistor. one is 100 V and second one is 250 V. so resistor value is (250 - 100) Volts / current flowing through it. $$R = V/I$$

nick67 · Answer

@vkp
didn't you take in account the capacitor discharge for 0.1 seconds ? (capacitor voltage falls below 250 V )  :-)
@maricarmendoza25
current value is not so clear: "the current flowing is 30/e Amperes"; could you clarify ?