# Voltage across resistors in RC circuit

• Qwurty2.0
In summary, the conversation discusses calculating the voltage, current, and power across two resistors for every second of run 1 in an RC circuit. The circuit is set up with a capacitor that is charged until it reaches 5.0V and then discharged until it reaches 1.0V, repeating this process four times. The conversation also mentions using the equations VC = ξ * (1 - e-t/RC) and RC=2secs to calculate the time constant and the voltage of the capacitor as it discharges. The expert advises redrawing the circuit and using the graph for a clearer understanding.
Qwurty2.0

## 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:

The settings of the circuit:

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.

## Homework Equations

VC = ξ * (1 - e-t/RC)

## 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.

...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.

## 1. What is a resistor in an RC circuit?

A resistor is a component in an RC circuit that is designed to limit the flow of electrical current. It is typically made of a material with high resistance, such as carbon or metal, and is used to control the amount of voltage across the circuit.

## 2. How is voltage measured across resistors in an RC circuit?

Voltage is measured across resistors in an RC circuit using a voltmeter. The voltmeter is connected in parallel to the resistor, allowing it to measure the potential difference between the two points.

## 3. What is the relationship between voltage and resistance in an RC circuit?

The relationship between voltage and resistance in an RC circuit is known as Ohm's Law. It states that the voltage across a resistor is directly proportional to the resistance, and inversely proportional to the current flowing through the circuit.

## 4. How does the voltage across a resistor change over time in an RC circuit?

In an RC circuit, the voltage across a resistor can change over time due to the presence of a capacitor. When the circuit is first connected, the capacitor will charge and cause a decrease in voltage across the resistor. As the capacitor becomes fully charged, the voltage across the resistor will increase until it reaches a steady state.

## 5. How can the voltage across a resistor be calculated in an RC circuit?

The voltage across a resistor in an RC circuit can be calculated using the formula V = V0(1 - e-t/RC), where V0 is the initial voltage, t is the time, R is the resistance, and C is the capacitance. This formula takes into account the charging and discharging of the capacitor over time.

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