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Please Help

Posted: Mon Jan 02, 2012 2:55 pm
by Adam
Was wondering if anyone could possibly help with this very simple question which I keep going round and round with but the sums do not seem to add up in terms of kechoffs V Law

Input V = 6V
Capacitor 1 = 2 Micro Farads
Capacitor 2 = 2 Capacitors in Parallel 1 @ 0.4 Micro Farads and 1 @ 0.6 Micro Farads

a) What is the total Charge into Network
b) What is the Charge associated with the 0.4 Micro Farad Capacitor
c) Calculate energy stored on 0.6 Micro Farad Capacitor
d) Calculate total Energy Stored.

Any help would be much apprecciated

Re: Please Help

Posted: Mon Jan 09, 2012 9:21 pm
by Thomas W
Is this the circuit you want to analyze?:

Re: Please Help

Posted: Tue Jan 10, 2012 5:55 pm
by Adam
That is exactaly the circuit I was wanting to analyze. Thankyou very much for the outstanding schematic but I realised I was being stupid and using the resistor formula for capacitors so all sorted now. Thanks very much for your help though.

Re: Please Help

Posted: Wed Jan 11, 2012 1:37 pm
by Thomas W
You're welcome - I'm glad you found a solution :)

Re: Please Help

Posted: Sat Feb 04, 2012 5:56 am
by appypaddy
I follow above circuit,I didn't get solution.

Any other soultions.

Re: Please Help

Posted: Sat Feb 04, 2012 6:09 pm
by Thomas W
a) Q = C * V (charge [C] = capacitance [F] * voltage [V])
Qtotal = Ctotal * Vin
Ctotal = 1 / ([1 / C1] + [1 / Cparallel])
Cparallel = C21 + C22 = 0.4 u + 0.6 u = 1 uF
Ctotal = 1 / ([1 / 2 u] + [1 / 1 u]) = 1 / (500 k + 1 M) = 1 / 1.5 M = 0.6667 uF
Qtotal = 0.6667 u * 6 = 4.000 u ~ 4 uC

b) c) ?

d) W = 0.5 * C * V² (energy [J] = 0.5 * capacitance [F] * voltage [V]²)
Wtotal = 0.5 * Ctotal * Vin² = 0.5 * 0.6667 u * 6² = 12.00 u ~ 12 uJ