Why is the equivalent capacitance in series smaller than the smallest individual capacitor?
In series, every capacitor carries the same charge Q, but the total voltage is the sum of each Q/C_i.
In series, every capacitor carries the same charge Q, but the total voltage is the sum of each Q/C_i. For a given Q the combination therefore needs more voltage than any one capacitor; since C_eq = Q/V_total, its capacitance must be smaller. Algebra says 1/C_eq = sum(1/C_i), which confirms the physical picture.
Key point
Series adds voltage requirements, so charge stored per total volt decreases.
Common mistake
adding capacitances directly as if they were parallel.
Memory tip
series: reciprocal, same charge.
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