Parallel
Capacitors - OCR A-Level Physics
- ParallelCapacitors connected in parallel share the same p.d.; total capacitance C = C₁ + C₂ + ...: each capacitor has the same p.d. but stores different chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Total chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). is the sum.
- SeriesCapacitors connected in series carry the same charge; 1/C_total = 1/C₁ + 1/C₂ + ...: each capacitor stores the same chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). but has different p.d. Total p.d. is the sum.
$$\begin{aligned}
\text{Parallel: } C_{\text{total}} &= C_1 + C_2 \qquad \text{Series: } \frac{1}{C_{\text{total}}} \\
&= \frac{1}{C_1} + \frac{1}{C_2}
\end{aligned}$$
Common Mistake
MEDIUM
Wrong: Treating capacitors in series like resistors in series (adding them directly).
Right: Capacitors in series combine like resistors in parallel (reciprocal sum), and capacitors in parallel combine like resistors in series (direct sum). The rules are the opposite way around to resistors.
Right: Capacitors in series combine like resistors in parallel (reciprocal sum), and capacitors in parallel combine like resistors in series (direct sum). The rules are the opposite way around to resistors.
Examiner Tips and Tricks
- For two capacitors in series, use the shortcut $C_{\text{total}$} = $\frac{C_1 C_2}{C_1 + C_2}$.
- Always check: the total series capacitanceThe charge stored per unit potential difference across a capacitor. Measured in farads (F). must be less than the smallest individual capacitanceThe charge stored per unit potential difference across a capacitor. Measured in farads (F)..