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# AQA Physics A Capacitor Question watch

1. "An initially uncharged capacitor of capacitance 10muF is charged by a constant current of 200muA. After what time willthe potential difference across the capacitor be 2000v?"

I figured Q = Q0 . e^(-t/RC)

But I wasn't sure what to do with the 'initially uncharged' part.

I worked out RC to be 100, by doing 10mu(2000/200mu), but I'm still confuseled as to whether I've done that wrong of it's a coincidence.
2. (Original post by Dalolguru)
"An initially uncharged capacitor of capacitance 10muF is charged by a constant current of 200muA. After what time willthe potential difference across the capacitor be 2000v?"

I figured Q = Q0 . e^(-t/RC)

But I wasn't sure what to do with the 'initially uncharged' part.

I worked out RC to be 100, by doing 10mu(2000/200mu), but I'm still confuseled as to whether I've done that wrong of it's a coincidence.
This question says "constant current" so there is no exponential charge or formula to worry about and no time constant.
Simply work out how much charge is on the capacitor when at 2000V using Q=CV
Then work out how long it would take a steady current of 200uA to deliver that much charge. Current is just charge per second.
You may by chance have got the right answer but not by the correct method.
3. Ahh thanks, I wondered why that part was in bold.

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