SESK: Stuff Everyone Should Know · sesk.info/eng-capacitor-blocks-dc
After it charges, how does a capacitor behave in a steady DC circuit?
Like an open circuit: no more current flows.
- Like a short circuit
- Like a fixed resistor
- Like an open circuit ✔
Why: A capacitor is two plates with an insulator between them. Current flows only while it charges, then stops. AC keeps charging and discharging it, so AC gets through.
Huh, didn't know that: Capacitive reactance is inversely proportional to frequency, so the higher the frequency, the more easily a capacitor passes it.
Why did the capacitor stop talking to DC? It had nothing left to say once it was charged.
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References
Answer: Like an open circuit. A capacitor is two plates with an insulator between them. Current flows only while it charges, then stops. AC keeps charging and discharging it, so AC gets through.
- OpenStax College Physics 2e, 23.11 Reactance, Inductive and Capacitive openstax.org/books/college-physics-2e/pages/23-11-reactance-inductive-and-capacitive
the current is zero once the capacitor is charged.
Checked 2026-10-10.
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