(adsbygoogle = window.adsbygoogle || []).push({}); Simple circuit problem.....

I was lookig at a circuit problem in a standardized test and I think the solution may be incorrect...

Here is the problem...

There is a battery (thus DC), a switch (open) and a resistor in series.....followed by a capacitor and a lamp in parallel.

The qusetion asks what happens when the switch is closed and gives the answer as" the lamp will flash on and off due to charging and discharging cycles of the capacitor"......this does not sound correct to me.

The answer I would give is as follows....

When the switch is closed at t=0+ the cap looks like a "short" (since it hasnt built up any resistance via the electric field) and all the current flows to the cap....so the lamp doesnt light.

As time goes on the cap charges and eventually all current to the capacitor stops. So the cap has some voltage across it, which means the lamp (resistor) also has that voltage across it since they are in parallel.

Thus, when the switch is closed, there will be a current flowing through the lamp effectively lighting it.

Now it is true that the cap will try to discharge through the lamp even when the switch is closed.....but wouldnt the discharge/charge time for the cap be so fast that there wouldnt be any noticable "flash" for the lamp while the switch is closed?

If anyone can tell me if I am off base here I would appreciate it.....

Thanks.

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# Simple circuit problem .

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