Voltage Across Capacitor

  • Thread starter roam
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  • #1
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Homework Statement



[PLAIN]http://img189.imageshack.us/img189/4555/capacitorh.jpg [Broken]


Homework Equations



[itex]I(t)=I_0 e^{-t/\tau}[/itex] (current as a function of time for a capacitor being charged)


The Attempt at a Solution



The time constant of the circuit is τ=RC=7s. And the initial current in the circuit is

v/Req=300/1489=0.2A (I know this is correct)

Now pluging into the equation:

[itex]I(5)=0.2 e^{-5/7}=0.0979 \ A[/itex]

[itex]V=IR= 0.0979 \ A \times 1489 \Omega = 145.73 \ V[/itex]

But the correct solution must be 153V. I'm very confused, what's wrong with my working? :confused:
 
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Answers and Replies

  • #2
ehild
Homework Helper
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1,909
Is V=IR the voltage across a capacitor???


ehild
 

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