Combination Capacitor Circuits

Key Questions

  • For capacitors in parallel:

    farside.ph.utexas.edu

    The total capacitance #C_(TOT# is given by:

    #C_(TOT)=C_1+C_2#

    Since #C_(TOT)=Q/V# the total can be found from #Q=C_(TOT)V# where V is the voltage drop across the capacitors.

    For capacitors in series:

    farside.ph.utexas.edu

    #1/C_(TOT)=1/C_1+1/C_2#

    So #Q=C_(TOT)V#

  • Series, parallel and combinations of series and parallel/


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    There are four examples of combinations in the diagram. The following points show how to calculate the total capacitance of each combination.
    1. Series
    The equivalent capacitance, C , of the combination is worked out as follows:

    #1/C=1/C_1+1/C_2+1/C_3#
    or
    #C=1/(1//C_1+1//C_2+1//C_3)#

    Total capacitance decreases in series.

    2. Parallel
    #C=C_1+C_2+C_3#

    Total capacitance increases in parallel.

    3. "Parallel in series"

    #1/C=1/C_1+1/(C_2+C_3)#

    4. "Series in parallel"

    #C=1/(1//C_1+1//C_2)+C_3#


    Example with numbers based on combination 4.

    #C_1=200muF#, #C_2=400muF#, #C_3=400 muF#

    #C=1/(1//(200*10^(-6))+1//(400*10^(-6)))+(400*10^(-6))#

    #⇒C=1/7500+400*10^-6=133*10^-6+400*10^-6#

    #C=533muF#

Questions