Question

Three capacitors with values 3, 4, and 5 micro facades (micro = 10^-6) are placed in series and hooked to a 12 V battery. (A) Find their equivalent capacitance and (b) find the charge on the 5 micro farad capacitor.

Answer 1

Remember:

For parallel combination

Ceq = C1 + C2 + C3 +...............

for series combination

1/Ceq = 1/C1 + 1/C2 + 1/C3 + ............

for 2 capacitors in series it will be

Ceq = C1*C2/(C1+C2)

Using this Information:

1/Ceq = 1/C1 + 1/C2 + 1/C3

1/Ceq = 1/3 + 1/4 + 1/5

1/Ceq = 47/60

Ceq = 60/47 = 1.28 uF

Now Qeq = Ceq*V

Qeq = 1.28*12 = 15.36 uC

Now remember in capacitors parallel combination voltage distribution in each part will be same and in series combination charge distribution in each capacitor will be same.

Since all capacitor are in serries, So charge on them will be equal to total charge

Charge on 5 uF = 15.36 uC

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