# Questions tagged [circuit-theory]

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### Can we solve all linear circuits using only KVL and constitutive relations?

Can We Solve for Node Voltages and Branch Currents in Any Linear Circuit Using Only KVL and Constitutive Relations? In circuits with a single loop, it's trivial to solve using only Kirchhoff's Voltage ...
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1 vote
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### Does KVL guarantee identical voltages/currents in similar circuits?

I have a question that is a bit abstract. Assuming I have two proper linear circuits, A and B, which have: The same ideal components (for example, voltage source, inductor, capacitor, resistor) The ...
• 250
121 views

### Power dissipation in an IC

Here is LM741 op amp circuit in Figure 1. The amplifier has two power supplies $V_{cc}$ and -$V_{ee}$. The up arrows are connected to the positive power supply $V_{cc}$ which is +15 V. Current ...
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1 vote
109 views

### Transient circuit analysis with additional source

The circuit in the image below is what I get when I open the switch of a larger circuit which I have already analysed. Therefore, I know the initial condition. simulate this circuit – Schematic ...
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104 views

### Are voltage ratings defined differently for capacitors and light bulbs?

The voltage rating of a capacitor is the maximum operating voltage, while the voltage rating of a light bulb is its normal operating voltage. Are there two different definitions of voltage ratings, or ...
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44 views

### How can I infer a circuit topology only from measuring/controlling its input and output?

Let's have a circuit only composed of resistors connected in a given topology. This topology (network) has a well defined boundary (input/output connectors) but otherwise we don't know how it is ...
148 views

### IV curve arithmetic - reference request

When playing around with electrical concepts in my head, I realized that the IV characteristic of any combination of elements, in series or in parallel, can be computed by simply adding the IV curves ...
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1 vote
257 views

### How to write the equation for the input side of a JFET?

I have been reading about the voltage gain of JFET, but I am unable to understand how to write the equation for the input side. Can somebody explain the method to write the equation for the input ...
• 147
159 views

### Resistive network with two voltage sources

Update: (I updated the description/Question for clarity) I am currently stuck trying to solve a seemingly simple resistive network. The voltages U1 and U2, aswell as Rr are known. The unknown ...
150 views

### Why doesn't mesh analysis work here?

I am new to theory of circuits and I just learned about mesh analysis. When I was doing some reviewing, I stumbled across this question and wonder if you can use it here: I plugged the equation into ...
1 vote
93 views

### Transient Charge Density in Conductor

Veritasium's (Derek Muller's) video How Electricity Actually Works makes the claim at 4:44 that: The truth is, if you average over a few atoms, you find the charge density everywhere inside a ...
• 25.3k
1 vote
57 views

### Computing input resistance of two common-base configurations

When computing the input resistance of this common base configuration, the collector current $I_C$ is approximated as equal to the emitter current $I_E$: simulate this circuit – Schematic ...
• 748
89 views

### Combining cable resistance and law of resistances in parallel circuits

For a parallel circuit it is true that $1/R = 1/R_{1} + 1/R_{2}$ Consider two equal cable switched parallel to each other. Their individual resistance is $R = phi * l * A$, where phi is constant. ...
• 103
3k views

### Does a resistor between two pairs of series resistors affect the equivalent resistance?

For the below DC circuit, does the 1Ω resistor in the middle have an effect on the equivalent resistance? If it does, how would you calculate the equivalent resistance? The rules for series and ...
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251 views

### How to find a missing resistor?

This seems to be a really simple question. I'm not really sure where I went wrong in my solution. Please forgive me if this seems irritatingly simple, I've only just started learning about electric ...
1 vote
248 views

### How to simplify this complex DC circuit?

I find it very hard to simplify this circuit. Currently practicing for my removal exam and this was one of the problems I failed on one of my previous exams. Especially the middle part makes me so ...
1k views

### What is the maximum current of an electronic load?

Here is the specification of an electronic load: If the load is set in current mode, the current is limited to 25 A. Nevertheless, if the current is set in resistor mode, I could think that it is ...
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121 views

### Good way to obtain voltages along (non-uniform) $RC$ line

I have a long RC line, e.g.: simulate this circuit – Schematic created using CircuitLab Is there a good way to obtain the voltages on nodes V1, ..., Vn (possibly approximated) at a specific ...
• 1,326
1 vote
616 views

### Synthesizing an impedance given by transfer function (poles/zeros) using a passive network

I would like to synthesize an arbitrary passive network based on a given transfer function (poles/zeros). The origin is the output impedance of a voltage regulator for which I want to find an ...
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182 views

### Transistor analysis with 2 voltage sources

I want to calculate the DC currents of this circuit, and based on the superpostion theorem, I thought of ignoring Vqdc9 first, in order to calulate I2, I21 and I22, as shown in figure 2. After that, I ...
419 views

### How do I use Norton's Theorem to find the current in this resistor? [closed]

I've been trying to solve this question but it seems impossible
262 views

### Mesh Current Method and Analysis DC

This is my approach so far: simulate this circuit – Schematic created using CircuitLab I'm having problems with the third loop, only because of the fact that there are two batteries that are ...
3k views

### Do higher voltages cause heating?

I'm trying to wrap my head around energy consumption in general. For some background info, I'm an engineering student and am familiar with the usual electrical engineering formulae Here is what caused ...
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189 views

### How do you prove that a certain circuit is impossible to construct with a certain amount of switches?

I wanted to make a subcircuit, which, if viewed as a black-box, is a two-terminal device, which can behave as a closed circuit (0 Ω) 25 Ω 50 Ω an open circuit (∞ Ω) (sans non-idealities of course; i....
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834 views

### Is it possible to constrain a circuit's voltage supply to a specific voltage range?

I have a circuit which requires exactly 12v to work properly, with a maximum tolerance of ±0.5V. The circuit is arbitrary and one can think of it as a theoretical question, but let's say that it ...
359 views

### Books on network theory [closed]

I really want to know which books should I read to learn the subject- Network theory in electrical engineering. I know there are some popular books out there in the market, but I will really ...
584 views

### Is reactive power periodic in nature? What is the exact difference between active power, average power, and real power?

Consider an RC circuit which is supplied by a sine source $$v(t)=V_m\cdot \sin(\omega t)$$ The current through the circuit will be i(t)=I_m\cdot \sin(\omega t+\phi) \\ \phi=\arctan \left(\dfrac{1}{\...
204 views

### Why reactive components have less influence at low frequencies?

Some textbooks state that reactive components (may) have less influence at low frequencies, since inductance and capacitance are generally more significant at hifh freqs. "Pratical electronics ...
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204 views

### Complex impedances of capacitors/inductors in the phasor domain

I'm trying to verify the complex impedances of passive components in the phasor domain (not s-domain). Take for example the inductor, whose element law is $v = L \frac{di}{dt}$. Assuming a complex ...
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1 vote
1k views

### dependent current source polarity

In this question, I apply the current cycle law, I find the current i1 to 25uA. I find the voltage on the dependent current source -2 volts. When I go through the formulas, there is no problem here. ...
• 756
200 views

### Transient solution of current in circuit with two coupled inductors, with resistances

Circuit in question is given below. I want to find why I can not get the same current waveform as PSpice gives me. Basically I want to calculate formula for i1(t) by hand and get something as close ...
• 41
577 views

### Why is this two-inductor circuit first order?

I have the following circuit with two inductors. Apparently this is a first order circuit (judging from my solutions for $i_1, i_2$; and circuit simulations) but it's not intuitively clear to me ...
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212 views

### Confusion Between Dual Capacitor/Inductor Circuits

I'm trying to physically understand the responses of this pair of (dual) circuits: a step current source driving a capacitor and a step voltage source driving an inductor. simulate this circuit &...
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### Relation between transmission line and circuit impedance

What is the relation between the impedance of lumped components and the characteristic impedance of transmission lines? I have noticed that in some cases transmission lines are loaded with lumped ...
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### Maximum error of nominal resistor combinations

Suppose you have resistors which have nominal values of $R_0$ or $2R_0$ but can vary to be anywhere between $(1 ± .03)R_0$ or $(2 ± .06)R_0$, respectively, so each can have about 3% error. ...
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142 views

### Linear Circuit and System Interpetation

My question is about interpreting a given circuit as being itself a linear system. We know that a linear system needs to satisfy the superposition principle: if $f(ax_1+bx_2)=af(x_1)+bf(x_2)$. This ...
• 675
1 vote
2k views

### Capacitor sign convention

I am a lot confused about how to assign the current of a capacitor and the sign of its constitutive relation, because usually in physics and in engineering there are different conventions. There are ...
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