Voltage across resistors in RC circuit

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SUMMARY

The discussion focuses on calculating the voltage, current, and power across two resistors in an RC circuit during charging and discharging phases. The capacitor charges to 5.0 V and discharges to 1.0 V, with the time constant determined to be 2 seconds. Participants clarified that the voltage across each resistor is not equal to the capacitor voltage at any given time, as they are connected alternately. The voltage across the resistors and the capacitor must sum to the total voltage in the circuit.

PREREQUISITES
  • Understanding of RC circuits and their components
  • Familiarity with the formula VC = ξ * (1 - e-t/RC)
  • Knowledge of voltage division in series circuits
  • Ability to interpret graphical data related to electrical circuits
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  • Learn how to derive the voltage across resistors in an RC circuit
  • Study the impact of time constants on capacitor discharge rates
  • Explore graphical analysis techniques for RC circuits
  • Review the principles of Kirchhoff's Voltage Law in circuit analysis
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Students studying electrical engineering, educators teaching circuit theory, and hobbyists working with RC circuits who need to understand voltage behavior across components.

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Homework Statement


Calculate the voltage, current, and power across the two resistors for every second of run 1 in the RC circuit.

The RC Circuit:
694ck0.png


The settings of the circuit:
r8xqhe.png


The Graph. The capacitor is charged until it reaches 5.0 V and then discharged until it reaches 1.0 V. This process occurs four times total.
v5czvb.png


Homework Equations


VC = ξ * (1 - e-t/RC)
(Not sure about others.)

The Attempt at a Solution


This is a lab more so than a question and therefore doesn't necessarily have an exact answer. I am having trouble with the process of getting an answer.

I have eyeballed the voltages from the graph for every second but am unsure how to calculate the voltage across each resistor. Is the voltage in each resistor the same as the voltage that is currently in the capacitor at time that time s?

I tried calculating the time constant by plugging the capacitor voltage at 5 seconds with a emf of 6.0 V and got 2.79 seconds, but 63% of 6.0 V is 3.78 V and eyeballing the graph I get approx. 2 seconds to reach 63% max voltage.

I feel like I am overthinking this and am unconfident in my knowledge of this section in my textbook, but rereading isn't helping me either.
 
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...am unsure how to calculate the voltage across each resistor. Is the voltage in each resistor the same as the voltage that is currently in the capacitor at time that time s?
No.
The each resistor is connected to the capacitor alternately (A-B-A-...) - so one resistor will have zero volts while the other has some non-zero voltage.
The voltage across the resistor and that of the capacitor, when they are connected, must add up to something.

I tried calculating the time constant by plugging the capacitor voltage at 5 seconds with a emf of 6.0 V and got 2.79 seconds, but 63% of 6.0 V is 3.78 V and eyeballing the graph I get approx. 2 seconds to reach 63% max voltage.
... the time constant is RC=2secs. Don't know what you were doing.

I feel like I am overthinking this and am unconfident in my knowledge of this section in my textbook, but rereading isn't helping me either.
You need to take another look at the circuit - maybe redrawing it to separate the charging and discharging stages - leaving out the components that do not contribute. It should become clear.
 
Simon Bridge said:
No.
The each resistor is connected to the capacitor alternately (A-B-A-...) - so one resistor will have zero volts while the other has some non-zero voltage.
The voltage across the resistor and that of the capacitor, when they are connected, must add up to something.

... the time constant is RC=2secs. Don't know what you were doing.

You need to take another look at the circuit - maybe redrawing it to separate the charging and discharging stages - leaving out the components that do not contribute. It should become clear.

Thanks, I was looking at the circuit wrong (I thought the charge was coming out the top and hitting the resistor after the capacitor).

Is there a way to calculate the voltage of the capacitor as it is discharging from 5V?
 
Thanks, I was looking at the circuit wrong (I thought the charge was coming out the top and hitting the resistor after the capacitor).
... it doesn't matter which order the current reaches the capacitor and the resistor.

Is there a way to calculate the voltage of the capacitor as it is discharging from 5V?
... yes, and you should have the equation in your course notes.
However - you should use the graph.
 

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