- #1
jaydnul
- 558
- 15
In a simple series RC circuit, when t=RC, the voltage across the resistor and capacitor is the same. Why is this physically significant and why do we choose this as the time constant that dictates the cutoff frequency?
Significance of RC time constant
- Thread starter jaydnul
- Start date
In summary: The time constant in the RC filter is useful for looking at ...The time constant in the RC filter is useful for looking at ...In summary, the time constant in an RC filter is a physical property that dictates the cutoff frequency.
- #2
nsaspook
Science Advisor
- 1,349
- 3,564
Review this first. We need some way to calculate the energy (as physical charge) in the capacitor over time into voltage or current values used in circuits.
- #3
jaydnul
- 558
- 15
Yes, but why is RC used when calculating cutoff voltage? If RC is arbitrary, then cutoff voltage is arbitrary which doesn't make sense to me.
- #4
berkeman
Mentor
- 67,058
- 19,876
Jd0g33 said:
I think you mean "cutoff frequency" like you posted in your Original Post, not some cutoff voltage...
And even "cutoff frequency" is a bit harsh to use for a simple single stage RC filter. A better term would be the -3dB frequency. Can you say why that would be a better term to use?
- #5
jaydnul
- 558
- 15
Ya sorry, cutoff frequency.
Is the -3dB arbitrary?
Is the -3dB arbitrary?
- #6
berkeman
Mentor
- 67,058
- 19,876
Jd0g33 said:
Well, you could pick -10dB or -20dB instead, so sure, it's semi-arbitrary.
But "RC" is simpler than "some number * RC", and RC gives you -3dB.
Your question is reasonable though. There are some things in physics and EE that are fundamental, and others that we use for convenience. It's fine to ask about the distinctions as you learn more and more in your education. This is a good place to ask such questions.
- #7
nsaspook
Science Advisor
- 1,349
- 3,564
The time constant in the RC filter is useful for looking at ...
Think about the electrical properties of an RC network and what -3dB means.
Jd0g33 said:
Think about the electrical properties of an RC network and what -3dB means.
- #8
jaydnul
- 558
- 15
Ok, thanks!
1. What is the RC time constant?
The RC time constant is a measure of the speed at which a capacitor charges or discharges in an RC circuit. It is calculated by multiplying the resistance (R) and the capacitance (C) of the circuit.
2. Why is the RC time constant important?
The RC time constant is important because it determines the rate at which a capacitor charges or discharges in an RC circuit. This is crucial in various electronic applications, such as timing circuits, filters, and signal processing.
3. How does the RC time constant affect the behavior of an RC circuit?
The RC time constant affects the behavior of an RC circuit by determining the time it takes for the capacitor to reach a certain percentage of its maximum charge or discharge. This, in turn, affects the frequency response and time-domain behavior of the circuit.
4. What is the relationship between the RC time constant and the time constant of an RL circuit?
The RC time constant and the time constant of an RL circuit are related in that they both measure the rate of change in current or voltage in their respective circuits. However, the equations used to calculate each time constant are different due to the different components used in each circuit.
5. How can the RC time constant be used in practical applications?
The RC time constant can be used in various practical applications, such as in timing circuits for electronic devices, in filters for signal processing, and in RC oscillators for generating precise frequencies. It is also used in RC networks for smoothing and stabilizing power supplies in electronic circuits.
Similar threads
-
Electrical Engineering
-
Electrical Engineering
-
Electrical Engineering
-
Engineering and Comp Sci Homework Help
-
Electrical Engineering
-
Electrical Engineering
-
Electrical Engineering