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Capacitance - urgent help please XD

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1. 2.0mF capacitor used as a backup power source. PD of 5.0V when fully charged.
Required to supply constant 1.0 microAmps and can be used until PD falls by 10%.
How long can it be used for?
2. V = Vnaught e^-t/rc

Use vnaught as 10% of v

rc we can calculate

use t = -(Ln(v/vnaught))RC
3. (Original post by Kyx)
V = Vnaught e^-t/rc

Use vnaught as 10% of v

rc we can calculate

use t = -(Ln(v/vnaught))RC
Thank you.
I thought of that but how can we work out RC if we don't have the resistance?
4. P = iv

p = v^2 / r

(Original post by myabzz)
thank you.
I thought of that but how can we work out rc if we don't have the resistance?
5. (Original post by Kyx)
P = iv

p = v^2 / r
Thank you, I think it is right
6. (Original post by myabzz)
Thank you, I think it is right
np

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