41 votes
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The Intuition for RLC circuits

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 it take to settle? Infinite time,...
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16 votes
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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}...
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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, ...
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14 votes
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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 ...
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14 votes
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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. ...
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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 ...
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13 votes
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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 ...
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12 votes
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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 ...
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11 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 ...
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LC Circuit problem!

200 V is indeed the correct answer, assuming ideal components. Think about this in the time domain. When the switch is initially closed, all the 100 V of the battery is applied across the inductor. ...
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10 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\...
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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 ...
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9 votes
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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 ...
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9 votes

Resonance of Parallel RLC circuit

Impedance is \$\dfrac{R + j\omega L}{R + j\omega L +\frac{1}{j\omega C}}\cdot\dfrac{1}{j\omega C}\$ = \$\dfrac{R + j\omega L}{j\omega RC + j^2\omega^2 LC +1}\$ = \$\dfrac{R + j\omega L}{j\omega RC - \...
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9 votes

Measure temperature on a moving engine valve: transfer voltage and reading wireless?

A good way might be to use a pyrometer. It is an optical device that receives the heat/light emitted by the object whose temperature needs to be measured and then uses part of that "spectra" to ...
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8 votes
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Why is series LC circuit not behaving as band pass filter?

That's the problem with simulating with "ideal" components — you see behaviors that you would never see in the real world. Your circuit has no resistance in it anywhere. The function generator ...
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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 ...
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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 / ...
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8 votes

The Intuition for RLC circuits

The corrected statement is that the slightly underdamped case has the shortest settling time. Now why is this the case when it's obvious that a highly underdamped system has a very long settling time?...
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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 \$\...
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7 votes
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Basic FM circuit

C3 turns the circuit into an oscillator. To understand this you need to think hard about the role of the emitter and the thing you have to think hard about is this - the emitter (as well as the base) ...
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7 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 ...
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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 ...
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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 ...
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7 votes
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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)}\$ ...
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7 votes
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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+...
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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 ...
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6 votes
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How to design a 4th/6th/8th passive low pass filter?

Your reasoning not to use an op-amp is basically flawed. here I quote you: - Of course a voltage follower will be applied at the output of the passive filter. This voltage follower can in fact ...
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6 votes
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Resonance frequency of an RLC circuit

KCL: (\$v_o\$ over your output, \$v_i\$ over voltage source and \$v\$ over the internal node: $$ \frac{v_o}{R_3} + \frac{v_o-v}{Z_{C1}}+\frac{v_o-v_i}{R_2} = 0 \\ \frac{v}{Z_L} + \frac{v-v_i}{Z_{C2}} ...
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6 votes

Resonance frequency of an RLC circuit

It is important to realize that the resonance frequency (i.e., the frequency at which the circuit resonates if the damping is sufficiently low) of a second-order RLC circuit never equals \$\frac{1}{\...
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