Skip to main content
44 votes
Accepted

The Intuition for RLC circuits

[!Quote] by a ConcernedCitizen Resistors are the electrical equivalent of friction and produce losses to remove energy from the system. If you drop a frictionless pendulum to swing it, how long does ...
DKNguyen's user avatar
  • 56.9k
16 votes
Accepted

Using a large resistor instead of a flyback diode

You need to be aware that the professor in the video is skipping over a few things. Note that at about 22 minutes, he writes the equation for the current through the resistor $$i = I_0 e^{\frac{R}{L}t}...
WhatRoughBeast's user avatar
16 votes
Accepted

What does the value of reactive power represent physically?

Let's ignore the power aspect for a second, and think about what reactance really is. You know a math and theory, you can talk about things in abstract theoretical constructs using complex numbers, ...
metacollin's user avatar
14 votes
Accepted

Using LC filter instead of RC filter in mains powered circuits

Ideal capacitors and inductors don't dissipate any power, whereas resistors do. One advantage is therefore that L-C filters are more efficient than R-C or R-L filters. Often it's not the actual ...
Olin Lathrop's user avatar
14 votes
Accepted

How do you determine the effective resistance of a finite grid of resistors?

The basic idea is fairly simple. You arrange a matrix (\$V\$) that represents "nodes" or vertices in your system. Each of these nodes has a scalar-valued "voltage" associated with it that can be ...
jonk's user avatar
  • 78.3k
14 votes
Accepted

Why is a linear passive circuit stable, i.e. why does its impulse response approach zero over time?

In a circuit that is composed of only Ls, Cs and Rs ... An input impulse will store energy in the Ls and Cs. The stored energy will be dissipated in the Rs, and will tend to zero over time. ...
Neil_UK's user avatar
  • 169k
14 votes

Why do I get this weird curve for impedance vs Frequency

Assuming the impedance is being calculated correctly, your problem is that you are starting at a low frequency (10 μHz) for which the impedance of your capacitor is very high (tens of megohms). The ...
Barry's user avatar
  • 16.1k
12 votes
Accepted

Understanding USB Inrush Current Requirements

The answer is: no one knows. Well, someone knows, but the inrush pass/fail test is considered proprietary information and how that determination is made is not published by the USB-IF, for reasons ...
metacollin's user avatar
12 votes
Accepted

Thevenin Equivalent Voltage: why ignore the 3-kΩ resistor?

Computing a Thevenin Equivalent requires two steps: Obtain the Thevenin Impedance \$Z_{TH}\$ Obtain the Thevenin Voltage \$V_{TH}\$ In order to compute \$Z_{TH}\$ you have to "turn off" the ...
Collado's user avatar
  • 236
11 votes

Why is a linear passive circuit stable, i.e. why does its impulse response approach zero over time?

I suspect the problem may arrive from the requirement of an impossible domain for passive component values. Your characteristic equation breaks down (as I'm sure you already know) into: \$\left(s+1\...
jonk's user avatar
  • 78.3k
10 votes

What does the value of reactive power represent physically?

When you have a complex load, its associated power can be modeled with a complex number: $$S = P+jQ$$ Where S is the complex power, usually measured in VA, P is the real power, measured in W, and Q ...
Vladimir Cravero's user avatar
10 votes

Thevenin Equivalent Voltage: why ignore the 3-kΩ resistor?

The Thévenin voltage is also known as the "open-circuit" voltage. In this case, the open circuit is between points A and B. Because it's an open circuit, no current flows through the 3k resistor, and ...
Shamtam's user avatar
  • 3,636
8 votes

Intuition for resonant, natural, and oscillatory frequencies of RLC circuits?

There are quite a few subtle differences between band-pass and low/high filters but, for a simple LCR band-pass filter, damped and un-damped resonant frequencies are the same numerically and ...
Andy aka's user avatar
  • 464k
8 votes
Accepted

Source-free, under-damped, parallel RLC with 2 intial conditions

Just to be complete: simulate this circuit – Schematic created using CircuitLab I gather that's the circuit. And you'd like an expression for \$V_{\left(t\right)}\$ and \$I_{L\left(t\right)}\$ ...
jonk's user avatar
  • 78.3k
8 votes

Thevenin Equivalent Voltage: why ignore the 3-kΩ resistor?

The Thevenin voltage is when the output terminals are open-circuit so any series resistance (3K in this case) has no effect. We can also ignore the 4K resistor since it's in series with a current ...
Spehro Pefhany's user avatar
8 votes
Accepted

Inductor and capacitor for energy storage instead of battery

...use a LC network to store small amount of electrical energy (500 mWHr or less) You might think that 0.5 WHr is "small" but for an LC tank, it is HUGE. So what is 0.5 WHr? 0.5 Watt = 0.5 Joule / ...
Bimpelrekkie's user avatar
8 votes

Am I on the right path to solve this RLC-Circuit? (Need to find the voltage at the resistor)

Yes, your analysis is correct. It would have been quicker to solve for the resistor current and then multiply through by \$\small R\$ to get the resistor voltage, \$v_R\$, as below (I've used \$\...
Chu's user avatar
  • 7,646
8 votes
Accepted

Parallel RLC time domain response, with two specified initial conditions and no driving source -- it is an homogeneous system

Question Recap I'd like to start with a quick recap taken directly from my question: $$\begin{align*} \frac{v_{_\text{C}}}{R_1}+C_1\frac{\text{d}}{\text{d}t}v_{_\text{C}}+\frac1{L_1}\int v_{_\text{C}}\...
jonk's user avatar
  • 78.3k
8 votes
Accepted

Inductor and Capacitor Timer - Strange behaviour: Need help understanding

I'll address myself to the simulator and mathematics, shortly. They match up. That won't answer your last question about what you observed when scoping out a circuit, though. But let's say that your ...
periblepsis's user avatar
8 votes
Accepted

Input filter LC for switching power supplies

With these types of filter I find that it's best to assume it will attenuate high-frequency noise based on a 1st order response (as if the inductor were replaced with a resistor) then, you put the ...
Andy aka's user avatar
  • 464k
8 votes
Accepted

How can these passive RLC circuits change a sinusoid's frequency?

There is no loss in the system, therefore the startup transient continues oscillating forever. (Due to numerical errors in the transient simulator, it won't actually go forever.) The measurement is ...
Tim Williams's user avatar
  • 39.2k
7 votes

Using LC filter instead of RC filter in mains powered circuits

LC noise filtering benefits were explained in other answers. This is an addition specific to triacs or thyristors. One reason to use an inductor in series with a triac is that a triac has maximum ...
dmitryvm's user avatar
  • 576
7 votes

What does the value of reactive power represent physically?

"Reactive power" is one of several possible ways of reconciling the fact that in AC systems, the voltage times the current isn't the average power. The reason rms(V) x rms(I) is not ave(V x I) is ...
Olin Lathrop's user avatar
7 votes
Accepted

How to sketch the Bode diagram of the output filter of a Buck converter?

Background Starting with your result and proceeding: $$\begin{align*} H\left(s\right)&=\frac{R}{R\,L\,C\,s^2+L\,s+R}\\\\ &=\frac{1}{L\,C\,s^2+\frac LR\,s+1}\\\\ &=\frac{\frac 1 {L\,C}}{s^2+...
jonk's user avatar
  • 78.3k
7 votes

Am I on the right path to solve this RLC-Circuit? (Need to find the voltage at the resistor)

As you could figure out, your source is expressed as a phasor, hence we can assume safely the solution can be expressed with phasors and impedances, in consistency with the requirement of ignoring ...
Brethlosze's user avatar
  • 1,427
7 votes
Accepted

LT Spice: parallel RLC circuit resonator giving weird frequency response?

This is a likely candidate for show-stopper of the month: - Then, when you fix that you'll realize that a voltage source (V1) is ideal and won't care a damn about C1 and L1 being present i.e. you'll ...
Andy aka's user avatar
  • 464k
7 votes

Input filter LC for switching power supplies

That's probably fine. A complete analysis requires much more information (voltage range, amount of ripple and noise, surge conditions if applicable, environmental, etc.), but these data likely don't ...
Tim Williams's user avatar
  • 39.2k
6 votes

Why is a linear passive circuit stable, i.e. why does its impulse response approach zero over time?

The simple answer is related to the Routh-Hurwitz stability criterion. This means that it simply doesn't matter how the terms of the polynomial end up as long as all the roots have negative real part. ...
a concerned citizen's user avatar
6 votes

How is this circuit providing solution of the differential equation d^2 v/dt^2 = -9v?

The output voltage v is the result of integrating twice. So whatever was before the integrating stages is d^2 v / dt^2 by definition. Since that node is driven strongly by the inverting gain stage, it ...
dnadlinger's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible