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Zorluk: ZorCapacitors and Capacitance

A 6 μF6\text{ }\mu\text{F} capacitor is connected in series with a parallel arrangement of a 2 μF2\text{ }\mu\text{F} capacitor and a 1 μF1\text{ }\mu\text{F} capacitor. If the entire circuit is connected across a 30 V30\text{ V} d.c. power supply, what is the electric charge stored on the 2 μF2\text{ }\mu\text{F} capacitor?

  1. A
    20 μC20\text{ }\mu\text{C}
  2. B
    30 μC30\text{ }\mu\text{C}
  3. 40 μC40\text{ }\mu\text{C}Cevap
  4. D
    60 μC60\text{ }\mu\text{C}

Cevap

The charge stored on the 2 μF2\text{ }\mu\text{F} capacitor is 40 μC40\text{ }\mu\text{C}.
To find the charge on the 2 μF2\text{ }\mu\text{F} capacitor, we first combine the parallel capacitors (2 μF+1 μF=3 μF2\text{ }\mu\text{F} + 1\text{ }\mu\text{F} = 3\text{ }\mu\text{F}). Next, we combine this in series with the 6 μF6\text{ }\mu\text{F} capacitor to get an overall capacitance Ceq=2 μFC_{eq} = 2\text{ }\mu\text{F}. The total charge drawn from the 30 V30\text{ V} supply is Q=2 μF×30 V=60 μCQ = 2\text{ }\mu\text{F} \times 30\text{ V} = 60\text{ }\mu\text{C}. This total charge enters the parallel combination, giving a potential drop across the parallel branch of Vp=60 μC/3 μF=20 VV_p = 60\text{ }\mu\text{C} / 3\text{ }\mu\text{F} = 20\text{ V}. Therefore, the charge on the 2 μF2\text{ }\mu\text{F} capacitor is 2 μF×20 V=40 μC2\text{ }\mu\text{F} \times 20\text{ V} = 40\text{ }\mu\text{C}.

Adım Adım Çözüm

1
Calculate the equivalent capacitance of the parallel section
Cp=2 μF+1 μF=3 μFC_{p} = 2\text{ }\mu\text{F} + 1\text{ }\mu\text{F} = 3\text{ }\mu\text{F}
Capacitors in parallel add directly.
2
Calculate the total equivalent capacitance of the network
Ceq=6×36+3=189=2 μFC_{eq} = \frac{6 \times 3}{6 + 3} = \frac{18}{9} = 2\text{ }\mu\text{F}
The 6 μF6\text{ }\mu\text{F} capacitor and the 3 μF3\text{ }\mu\text{F} parallel equivalent are in series.
3
Find the total charge supplied by the 30 V30\text{ V} source
Qtotal=Ceq×V=2 μF×30 V=60 μCQ_{total} = C_{eq} \times V = 2\text{ }\mu\text{F} \times 30\text{ V} = 60\text{ }\mu\text{C}
Total charge is the product of equivalent capacitance and total voltage.
4
Determine the potential difference across the parallel branch
Vp=QtotalCp=60 μC3 μF=20 VV_{p} = \frac{Q_{total}}{C_{p}} = \frac{60\text{ }\mu\text{C}}{3\text{ }\mu\text{F}} = 20\text{ V}
The total charge flows through the series combination, creating a potential drop across the parallel combination equal to Qtotal/CpQ_{total} / C_{p}.
5
Calculate the charge on the 2 μF2\text{ }\mu\text{F} capacitor
Q2μF=C2μF×Vp=2 μF×20 V=40 μCQ_{2\mu\text{F}} = C_{2\mu\text{F}} \times V_{p} = 2\text{ }\mu\text{F} \times 20\text{ V} = 40\text{ }\mu\text{C}
The charge on a specific capacitor in parallel is the product of its capacitance and the voltage across the parallel branch.

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