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# charge response for delta input..

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#### transgalactic

##### Banned
i have a current source
I(t)=delta(t)
connected in parallel with with a capacitor of 1F and the capacitor is
connected in parallel with a ressistor
for which in t<0 its R(t)=1 ohm
and in t>=0 its R(t)=t+1 ohm
i need to find charge response for delta input for every point in time
usually what i do is make KCL on the central node and say that the potential on
that node is Vc
-Is+Ic+Ir=0

delta(t)=1(Vc)' +(Vc)/R
etc..

first of all i dont know whats charge response
but in the solution i see an equation
delta(t)=(q)' +q/(CR(t))

i know that Q=CV
and that I=(Q)'

but both of those formulas are for capacitator.
altough one of the currents goes to the resistor
which has nothing to do with a capacitator
??

Hi,

Does it help if you think about the 'charge' as only being present in the
capacitor? In other words, forget about the resistor when it comes to charge
and try to solve the problem in terms of charge in the capacitor. Of course
the resistor is in the circuit too so that will affect the charge in the capacitor
too.

Last edited:
i cant see on what basis they say that
Vc=q

i dont know where tolook for that charge response

i didnt find similar things in google

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