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I have a question about capacitors. In the circuit below, capacitor C2 is in parallel with a wire. When a resistor is connected in parallel to a wire, the potential across it equals zero so no current goes through it. My questions are does the potential difference across C2 equal zero because it's in parallel with a wire? And if so, does the capacitor not get charged (Q=0) and does it not contribute to the capacitance of the circuit (C of whole circuit just = C1)? enter image description here

Lastly, if the potential difference equals zero, could you draw an equivalent circuit by just removing C2 (like shown below)? enter image description here

Thank you!

christina
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2 Answers2

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My questions are does the potential difference across C2 equal zero because it's in parallel with a wire?

Correct.

Imagine if the potential difference were (say, at some instant in time) not zero. What would the wire do? What would happen to the charge on the capacitor?

And if so, does the capacitor not get charged (Q=0) and does it not contribute to the capacitance of the circuit (C of whole circuit just = C1)?

Correct. $Q=CV$, so if $V = 0$, then there's no charge separation on the capacitor.

The Photon
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  • Can you check my intuition here; since there isn't any resistance to current given by an ideal capacitor, you'd think that current wouldn't differentiate between a wire and a capacitor in the initial instant, and that this current would flow through the capacitor. But when the slightest charge is induced on the capacitor, it offers more resistance to current than the wire, so current goes through just the wire. Is that right? – harry Mar 19 '21 at 04:26
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It's a really bad thought, but here it is, current wants minimum potential drop in its way, if there was a resistor similar thing would have happened . The current has a alternate route with zero pd drop, so it chooses that route

kedar Salunkhe11
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