RC Circuit with alternating voltage source

In summary, the conversation discusses finding the current in a circuit with a voltage source, capacitor, and resistor in series. The equation I = C*dv/dt is used and it is clarified that v refers to the voltage across the capacitor. The use of Kirchhoff's Voltage Law is also mentioned. It is suggested to use the phasor representation of the voltage source, V = V0ejwt, and deal with the real portion of the resulting voltage.
  • #1
sun18
16
1

Homework Statement


I'm supposed to find the current in a circuit with a voltage source, capacitor, and resistor in series. The voltage source is described by V=V0ejwt.
Here, j is the complex number j2=-1, and i is the current

Homework Equations


I=C*dv/dt

The Attempt at a Solution


I have several sources of confusion with this question. First, in the equation I=C*dv/dt, does that v refer to the voltage source, or specifically the voltage drop across the capacitor? Can I use Kirchoff's voltage law with this type of circuit? I tried this and got:

V0ejwt - iR - q/c = 0
Then taking the time derivative of the equation:

V0jwejwt - R*di/dt - i/c = 0
I then have no idea how to solve this differential equation. Even rewriting with euler's identity:
V0jw[cos(wt)+jsin(wt)]=R*di/dt+i/c

Any help would be greatly appreciated.
 
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  • #2
I suspect that the ##V = V_o e^{j \omega t}## is meant to be a phasor representation for the input. Have you covered phasors yet? If so you're meant to deal with the real portion of the resulting voltage, which in this case would be ##V_o cos(\omega t)##.

Yes, the v in I = C*dv/dt represents the voltage across the capacitor.

Yes, Kirchhoff's Voltage Law (KVL) can be applied as you have done.
 
  • #3
We haven't covered phasors yet but I read ahead and it makes sense now.
Thank you for the response.
 

1. What is an RC circuit with an alternating voltage source?

An RC circuit is a type of electrical circuit that consists of a resistor (R) and a capacitor (C) connected in series with an alternating voltage source. The alternating voltage source provides varying voltage levels that alternate between positive and negative values over time.

2. How does an RC circuit with an alternating voltage source work?

When the alternating voltage source is connected to the RC circuit, the capacitor charges and discharges in response to the changing voltage levels. This results in a time-varying current flowing through the circuit, which can be used to power devices or perform other functions.

3. What is the time constant of an RC circuit with an alternating voltage source?

The time constant of an RC circuit is a measure of how quickly the capacitor charges and discharges in response to the alternating voltage. It is calculated by multiplying the resistance (R) and capacitance (C) values in the circuit, and is typically denoted by the symbol τ.

4. How is the time constant related to the frequency of the alternating voltage source?

The time constant is inversely proportional to the frequency of the alternating voltage source. This means that as the frequency increases, the time constant decreases, and vice versa. This relationship is important in understanding the behavior of an RC circuit with different frequency inputs.

5. What are some practical applications of an RC circuit with an alternating voltage source?

RC circuits with alternating voltage sources have a variety of applications, including in power supplies, signal filters, and timing circuits. They are also commonly used in electronic devices such as radios, televisions, and computer circuits. Additionally, they can be used for scientific experiments and demonstrations to study the behavior of capacitors and alternating currents.

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