# Resistors and capacitors

I got a question that reads: Supoose a 10khz signal with an amplitude of 1 volt is applied across a 1k(ohm) trdidyot snf s 0.25 microF capacitor which are connected in series. What is the voltage drop across the capacitor?

I tried to use the equation Vc(t) + Vco*cos(omega*t) in which i got 1*cos(2*pi*10000*0.0025) in which i got -.92104. I don't think this is right, but i am not sure.

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Tom Mattson
Staff Emeritus
Gold Member
Help me get this straight: You've got a single loop circuit with a voltage source, a resistance, and a capacitance, is that it?

If that's the case then you can write down Kirchhoff's voltage law for the loop. You'll have a first order differential equation which you can solve for the capacitor voltage.

so the answer would be 1 since i would do 1volt(1kohms/1kohms)=1v?

Tom Mattson
Staff Emeritus
Gold Member
Think about what you've just said. You've got a capacitor with a resistance hooked up to a time-varying voltage source. How can you have a constant voltage across the capacitor in that case? (Answer: You can't.)

Am I correct in my assumption about the setup of this circuit?

Tom Mattson said:
Think about what you've just said. You've got a capacitor with a resistance hooked up to a time-varying voltage source. How can you have a constant voltage across the capacitor in that case? (Answer: You can't.)

Am I correct in my assumption about the setup of this circuit?
yes i beleive you are correct. I copy the question just like it is in my pre lab.

Tom Mattson
Staff Emeritus