Basic RC circuit question

nora's picture

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Joined: Feb 20, 2021

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Basic RC circuit question
February 21, 2021 - 12:04am

Hi. I'm new to electronics, hence the basic question.

When a load such as a lamp is placed in parallel with a capacitor in a basic RC circuit, why doesn't current flow through the lamp while the capacitor is charging? The virtual simulator i am using shows no current through the lamp until the capacitor is fully charged. Why wouldn't there be some current divided between both the capacitor branch and the lamp, and then just the lamp when the capacitor is fully charged?

Thanks for your help.

Sourav Gupta's picture

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Joined: Feb 12, 2018

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You need to provide the schematic. Is the lamp acting as the R in RC circuit? Parallel RC circuit or the lamp is in parallel of series RC circuit?

Virtual simulator provides output based on ideal state of the comonent. In real life the thing is different.

Harry's picture

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Joined: Feb 15, 2021

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The capacitor affects the rise time. Too see this in a simulator you must use pulses.

I would show you a capture from the simulator but I see no way to upload an image in this basic forum.

Sourav Gupta's picture

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Capacitor has low ESR resistance than the lamp. Providing images would be beneficial. Use the IMCE button in the toolbar to upload images.

Thank you.

nora's picture

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Joined: Feb 20, 2021

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I can't see the imce button on mobile, but just to add, I'm using an led and not a lamp. Not sure if that changes anything? I can see it takes about 40ms for the led branch to get to 1.8v and then the current flows, whereas the parallel capacitor branch current flows the instant the switch is closed. I will upload an image when I get back on my work computer. Thanks for all your help.

Sourav Gupta's picture

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Well, Capacitor has very low resitance called as ESR than the diode.