How do Resistors and Capacitors behave in parallel circuits?

In summary, when a resistor is in parallel with a capacitor, the current through the resistor will stay the same, while the current through the capacitor will decrease after the switch is opened.
  • #1
lollol
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0
I get very confused when you have circuits involving Capacitors and Resistors

Especially the concept of current traveling through the path of least resistance

1) Let's say you have a circuit with a battery... with a resistor in parallel first, then a capacitor in parallel to the resistor.. does the current NOT pass thru the resistor at all.. since the capacitor route has no resistance?

I've included an image called CIRCUIT 1

2) Let's say you have the following scenario in CIRCUIT 2... diagram is provided... what happens when you close the switch?? does all of it pass into the capacitor ? or if it splits, how does it split :(

Is there a simple conceptual way to understand these rules so that I don't have to keep memorizing what happens with diff. scenarios
 

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  • #2
lollol said:
I get very confused when you have circuits involving Capacitors and Resistors

Especially the concept of current traveling through the path of least resistance

1) Let's say you have a circuit with a battery... with a resistor in parallel first, then a capacitor in parallel to the resistor.. does the current NOT pass thru the resistor at all.. since the capacitor route has no resistance?

Well, the images are waiting for approval, yet, but I can say the current through the resistance is independent of the current through the capacitor, since it depends only on the resistance and battery values.
 
  • #3
lollol said:
Especially the concept of current traveling through the path of least resistance
This phrase has little value in circuit analysis. Current always travels through all paths, not just the path of least resistance. The goal of circuit analysis is to determine exactly how much current goes through each path.
 
  • #4
If you go ahead and actually hook up such a circuit and put ammeters in each branch, you'll see the resistor current go to a stable value almost immediately and then stay there. You'll see the capacitor current go to a peak value and then fall slowly toward zero (if you use a good digital meter, you'll be able to see how it approaches zero and that's interesting).
 
  • #5
Those circuits don't exist. You can't made such a circuit. The wires, the battery and the capacitor have resistance and inductance.
You can analyze what happens if you connect real batterys to real capacitors but you must take into account the resistance, that is not 0.

In fig.1 a capacitor that is connected to a battery ( you didnt draw the switch, but I suppose there is a switch ) draws infinite intensity.

In fig.2 there is a short-circuit -> infinite intensity.
 
  • #6
I'm just confused as to what happens in a situation where a resistor is in parallel with a capacitor

The only scenario I can understand so far is: what happens when a resistor is in series with a capacitor. That's it.
 
  • #7
lollol said:
I'm just confused as to what happens in a situation where a resistor is in parallel with a capacitor

The only scenario I can understand so far is: what happens when a resistor is in series with a capacitor. That's it.

The thing you need to always remember is that parallel circuits are essentially independent. (I am speaking here of voltage circuits). In a manner of speaking, the computer I am writing this on is possibly in parallel with the radio you might be listening to right now. So, the current through the parallel resistor is independent of the current into the parallel capacitor, etc. So, this allows you to look at parallel circuit branches as though they were little isolated circuits, provided you can figure out the voltage for that branch (usually the same in simple circuits). If you possibly can take a lab course in this, do so. It helps immensely to actually see this stuff.

Anyway, the most important thing a resistor in parallel with a capacitor does is drain off the capacitor charge after the switch is opened. Keeps you from getting a shocking experience.
 

1. What is an RC circuit and how does it work?

An RC circuit is a type of electrical circuit that consists of a resistor (R) and a capacitor (C) connected in series or parallel. The resistor limits the flow of current, while the capacitor stores electrical charge. When a voltage is applied to the circuit, the capacitor charges up and then discharges through the resistor, creating a time-varying current. This process continues until the capacitor reaches its maximum charge or the voltage source is removed.

2. What is the purpose of an RC circuit?

The purpose of an RC circuit is to control the flow of electrical current and create a time delay in a circuit. RC circuits are often used in filters, timers, and oscillators in electronic devices.

3. How do I calculate the time constant of an RC circuit?

The time constant (τ) of an RC circuit can be calculated by multiplying the resistance (R) in ohms by the capacitance (C) in farads. The formula is τ = R x C. The time constant represents the time it takes for the capacitor to charge up to 63.2% of its maximum charge.

4. What is the difference between a series and parallel RC circuit?

In a series RC circuit, the resistor and capacitor are connected end to end in a single loop, while in a parallel RC circuit, they are connected side by side with a common voltage source. The main difference is in the way the components are connected, which affects the current and voltage in the circuit. In a series RC circuit, the current is the same through both components, while in a parallel RC circuit, the voltage is the same across both components.

5. How does the frequency of the input voltage affect an RC circuit?

The frequency of the input voltage affects an RC circuit in several ways. At higher frequencies, the capacitor has less time to charge and discharge, resulting in a smaller time constant and a faster response time. Additionally, the impedance (resistance) of a capacitor decreases as the frequency increases, allowing more current to flow through the circuit. This can impact the overall behavior and performance of the RC circuit.

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