If you wire two 20-microfarad capacitors in series, what is the capacity of the combination?

Capacitors behave exactly opposite to resistors and inductors when it comes to series and parallel wiring. When capacitors are wired in series, the total capacitance decreases. This is because placing them in series effectively increases the distance between the outermost plates, which lowers the overall ability to store a charge. The formula for capacitors in series is 1/C_total = 1/C1 + 1/C2. If you have two identical capacitors in series, the total capacitance is exactly half of a single capacitor's value. Therefore, two 20-microfarad capacitors in series will yield a combined capacity of 10 microfarads. You would only get 40 microfarads if they were wired in parallel.