A C=0.1µF (1µF=10-6F) capacitor is arranged so that a constant (does not depend on time) current of I=2 µA (1µA=10-6A) flows toward the top electrode, and away from the bottom electrode. How long will it take to charge the capacitor to 10V?

Respuesta :

Answer:

0.5 seconds

Explanation:

Charge

[tex]Q=CV\\\Rightarrow Q=0.1\times 10^{-6}\times 10\\\Rightarrow Q=0.000001\ F[/tex]

Resistance

[tex]R=\dfrac{V}{I}\\\Rightarrow R=\dfrac{10}{2\times 10^{-6}}\\\Rightarrow R=5000000\ \Omega[/tex]

We have the relation

[tex]Q=CV\left(1-e^{-\dfrac{t}{RC}}\right)\\\Rightarrow 0.000001=0.000001\left(1-e^{-\dfrac{t}{5000000\times 0.1\times 10^{-6}}}\right)\\\Rightarrow \dfrac{0.000001}{0.000001} = \left(1-e^{-\dfrac{t}{5000000\times 0.1\times 10^{-6}}}\right)\\\Rightarrow \dfrac{0.000001}{0.000001}-1=-e^{-\dfrac{t}{5000000\times 0.1\times 10^{-6}}}\right)\\\Rightarrow 0=e^{-\dfrac{t}{0.5}\right)\\\Rightarrow -\dfrac{t}{0.5}=1\\\Rightarrow -t=0.5\ s[/tex]

The time taken is 0.5 seconds