When different rated capacitors are connected in series in a circuit, the total capacitance is

• A. Equal to the sum of all the capacitances.
• B. Greater than the capacitance of the highest rated capacitor.
• C. Less than the capacitance of the lowest rated capacitor.
• D. Equal to the average of the capacitances.

Answer: (C)

In series, the total capacitance is smaller than the smallest capacitor in the string. This happens because the same charge flows through each capacitor, so the voltages across them add up as V_total = V1 + V2 + …, and each voltage is Q/Ci. The combined effect is captured by 1/Ceq = 1/C1 + 1/C2 + …, which makes Ceq smaller than any individual capacitance (strictly smaller if there are two or more capacitors). For example, 4 µF and 6 µF in series give Ceq = (4×6)/(4+6) = 2.4 µF, which is less than both. Therefore the total capacitance in series is less than the lowest-rated capacitor in the group.