Why is the current passing through a capacitor in RC circuit (in steady state) considered to be zero?
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$\begingroup$ In AC steady state, it's not considered zero. In DC steady state it's zero because a capacitor doesn't provide a path for DC current flow. $\endgroup$– The PhotonCommented May 8, 2017 at 14:39
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$\begingroup$ Think of it how could current flow through a capacitor? AC can fluctuate back and forth on the connecting wire without charges jumping across the capacitor plates but the DC must go through, right? But when that happens it is not a capacitor anymore. $\endgroup$– hyportnexCommented May 8, 2017 at 15:06
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2 Answers
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The current does not actually pass through a capacitor rather current enters and leaves a capacitor resulting in the amount of charge which is stored by the capacitor changing.
In steady state the amount of charge stored by the capacitor is not changing so no current (flow of charge) has to flow in or out of the capacitor.
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Initially when the switch is closed then due to potential difference the electron flows and it accumulates on the negative plate and due to the law of conservation of charge, same amount of charge depletes from the positive plate , and in this way positive and negative charge develops on the plates. Now as the charges develops the potential difference is created due to the electric field between the plates. The rate of flow of charges i. e, current decreases because of accumulated charges on the plates repels the incoming charges. In the steady state, The potential difference across the capacitor plates equals the applied voltage and is of opposite polarity. So current becomes zero. We can visualize the charging capacitor as a variable voltage source . In steady state the voltage across the plates become equal to the applied voltage.
