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Capacitance

Capacitors in series and in parallel

  • 3 things to know
  • Component 2

Overview

Equation for the combined capacitance of capacitors connected in parallel and equation for the combined capacitance of capacitors connected in series.

What you need to know

Answer each one before you reveal it.

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Key term

Derive the rule for capacitors in parallel.

Key term

Derive the rule for capacitors in series.

Key term

Why do capacitors in series all carry the same charge?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State the equation for the combined capacitance of capacitors connected in parallel.

    Model answer

    For capacitors in parallel the combined capacitance is C = C₁ + C₂ + C₃ + … .

  2. 2

    State the equation for the combined capacitance of capacitors connected in series.

    Model answer

    For capacitors in series the combined capacitance is given by 1/C = 1/C₁ + 1/C₂ + 1/C₃ + … .

  3. 3

    Derive the rule for capacitors in parallel.

    Model answer

    Capacitors in parallel all have the same potential difference V, and the total charge is Q = C₁V + C₂V + … . Since the total charge is also CV, dividing throughout by V gives C = C₁ + C₂ + … .

  4. 4

    Derive the rule for capacitors in series.

    Model answer

    Capacitors in series all carry the same charge Q, and the potential differences add, so V = Q/C₁ + Q/C₂ + … . Since V is also Q/C, dividing throughout by Q gives 1/C = 1/C₁ + 1/C₂ + … .

  5. 5

    Why do capacitors in series all carry the same charge?

    Model answer

    The section of circuit between two capacitors in series is isolated, so any charge that leaves one plate must arrive on the plate facing it, and the plates are charged equally throughout the chain.

  6. 6

    Why does connecting capacitors in parallel increase the total capacitance?

    Model answer

    The plate areas are effectively added together, so more charge is stored for the same potential difference.

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