A 187 mu F capacitor is fully charged by connecting it to a

A 18.7 mu F capacitor is fully charged by connecting it to a 13.0 V battery. Calculate the charge stored on one of the capacitor plates. This charged capacitor is now disconnected from the battery, and connected to a different capacitor C that is initially uncharged. The resulting final voltage of each capacitor is 2.40 V. Determine the capacitance C.

Solution

a) Q = C V

= 18.7 * 10^-6 * 13.0

= 0.0002431 C = 243.1 muC

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b) Q = C V = 18.7 * 10^-6 * 2.4 = 0.00004488 C = 44.88 muC

243.1 - 44.88 = 198.22 muC

C = Q / V = 198.22 / 2.4

= 82.59 F