CIE A Level Physics (9702) 2019-2021

Revision Notes

22.1.3 Capacitors in Series & Parallel

Capacitors in Series & Parallel

  • Recall the formula for the combined capacitance of capacitors in series:

  • In parallel:

Ctotal = C1 + C2 + C3

Worked example: Calculating total capacitance between two points

Capacitors_in_Series___Parallel_Worked_Example_-_Capacitors_in_Series___Parallel_Question, downloadable AS & A Level Physics revision notes

Step 1:            Calculate the combined capacitance of the two capacitors in parallel

                        Capacitors in parallel: Ctotal = C1 + C2 + C3

Cparallel = 23 + 35 = 58 μF

Step 2:            Connect this combined capacitance with the final capacitor in series

Step 3:            Rearrange for the total capacitance

Exam Tip

Both the combined capacitance equations look similar to the equations for combined resistance in series and parallel circuits. However, take note that they are the opposite way around to each other!

Capacitors in Simple Circuits

  • Capacitors can be connected in series or parallel just like most electrical components in simple circuits
  • However, the combined capacitance will vary depending on whether they are connected in series, parallel or a mix of the two
    • This is called a network of capacitors
    • This is similar to combining resistors
  • Some functions of capacitors in simple circuits are:
    • To store energy
    • To separate charge
    • In smoothing
    • To block D.C
    • To produce electrical oscillations
    • To prevent electric sparks
    • In timing circuits

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