# How Does DC Current Charge a Capacitor?

There is something I can't grasp regarding capacitors. Say for example I'm using a simple rc circuit that has one 5v dc power source, a resistor, and a capacitor. The capacitor will charge until it reaches 5v, then cut all current. What I don't understand is how the capacitor can receive the charge in the first place? Isn't a capacitor effectively an open circuit, therefore there shouldn't be any flow and the capacitor shouldn't be able to charge in the first place? Isn't it analogous to a switch that is in the open state in a circuit?

• If the capacitor is charging, then by definition you have a time-varying voltage in your circuit, which is not DC. Connecting the battery is equivalent to applying a step function. Again, not DC. Commented Sep 27, 2018 at 20:53
• Current doesn't flow through the capacitor - the dielectric is an insulator. Charge flows onto the plates. As the charge builds up, so does the voltage across the capacitor, and the direct current reduces since the voltage across the series resistor decreases; falling to zero when the capacitor is fully charged.
– Chu
Commented Sep 27, 2018 at 23:49