Problem 24.61 Three capactors having capacitances of 8.8 pF, 8.1 NF and 5.0 RF a

Question

Problem 24.61 Three capactors having capacitances of 8.8 pF, 8.1 NF and 5.0 RF are connected In Berles across a 30-v potential Part A NF capacitor? Express your answer ualng two algnificant figures. Qa- 6.9x or C MLAnworc Give up Part B Express your answer ualng two algnificant figures. U- 1.0x10 J MLAnworc Give up Part C Express your answer ualng two algnificant figures. v- 3.1 Incorrect: Try Again: 4 attempt remaining Part D Express your answer ualng two algnificant figures. They are then reconnectedIn parallel wm each other. positively Whatlethe voltage across each capacorn the paralel combinaton?

Explanation / Answer

A) in series combination, net capacitance,

1/Cnet = 1/8.8 + 1/8.1 + 1/5

Cnet = 2.288 micro F

so, charge on each capcitor,

Qnet = Cnet*V

= 2.288*30

= 6.9*10^-5 C

B) U_total = 0.5*Cnet*V^2

= 0.5*2.288*10^-6*30^2

= 1.03*10^-3 J

C) when they are connected in prallel, charge on positive plates will be,

Qnet = 3*6.9*10^-5

= 2.07*10^-4 C

net capaciatnce, Cnet = C1 + C2 + C3

= 8.8 + 8.1 + 5

= 21.9 micro F

so, potential across them, V = Qnet/Cnet

= 2.07*10^-4/(21.9*10^-6)

= 9.45 volts

D) U_total = 0.5*Cnet*V^2

= 0.5*21.9*10^-6*9.45^2

= 9.8*10^-4 J

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