Just need help with part C. I have seen all the other examples but unfortunately
ID: 1437071 • Letter: J
Question
Just need help with part C. I have seen all the other examples but unfortunately I don't understand the math in the last step. Thanks for your help.
(a) A 44 resistor is connected in series with a 7 µF capacitor and a battery. What is the maximum charge to which this capacitor can be charged when the battery voltage is 9 V? (When entering units, use micro for the metric system prefix µ.)
(63 microC is correct)
(b) Initially the capacitor has zero charge. At what time during the charging process will the charge on this capacitor be 39.8 µC?
(3.079e-4 s is correct)
(c) The capacitor is now fully charged. The battery is removed and the capacitor is discharged through a bulb. What will be the charge on the capacitor after 0.308 ms? (Assume that the bulb has the same resistance as the original resistor.)
Explanation / Answer
The discharge voltage follows the equation:
V = Vb*e^-(t/RC)
V = Vb*e^-1 = 9*e^-1 = 3.3 V
Q = C*V = 7*10^-6 * 3.3 = 23.2*10^-6 C = 23.2 µC
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