AC1 Fundamentals Unit 6 – Capacitance
A capacitor charges when dc is applied to it. While the capacitor is charging, current flows until
the capacitor is fully charged. At that time, current flow stops and the voltage across the
capacitor equals the applied dc voltage.
Therefore, a capacitor blocks dc current when fully charged. As you continue your study of
electronics, you will see that the ability to block dc is very useful.
A capacitor will not block ac current because the voltage level and polarity are constantly
changing.
Although ac passes through a capacitor, the capacitor does create opposition (impedance) to
current flow. This impedance depends on the value of the capacitor and the frequency of the
applied signal.
Total capacitance decreases as the number of capacitors in series increases.
Total capacitance increases as the number of capacitors in parallel increases.