Questions tagged [equation]

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32 views

Calculating inductance of inductor that has ferrite core and a large air gap

I'm working on a coil on a PCB that will have a small ferrite core place in the center, with a large gap. I'm trying to come up with a decent equation to estimate the inductance of this inductor. I'...
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2answers
72 views

Solving simple parallel/series without Req

Given the following circuit with three resistors, R1=100Ω, R2=200Ω, R3=300Ω: To solve this using the \$R_{eq}\$ trick: ...
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2answers
62 views

Number of independent KVL and KCL

I know that the number of KTL and KCL is related to the number of nodes \$N\$. For KCL there are \$N-1\$ equations while for the KTL there are \$L-(N-1)=L-N+1\$ equations. However I didn't understand ...
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26 views

Capacitance of parallel wires in checkerboard pattern

Below is a cross-sectional view of a 4x4 array of inter-meshed cylinders... $$\begin{matrix}\Huge\circ && \Huge\bullet && \Huge\circ && \Huge\bullet \\\\ \Huge\bullet &&...
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27 views

Voltage variation and electrical fields Maxwell Equations

I actually know without knowing the reason or the mathematical expression of the physical phenomenon, that if we apply accross a capacitor a voltage which varies in function of the time, it produces ...
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2answers
63 views

State variable equations for a RLC circuit

What are the state variable equations of this RLC circuit? How do I write the final matrix? I tried to write the equations for the capacitor and inductor: $$L\frac{di_3}{dt}=v_1-v_C \leftrightarrow \...
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1answer
106 views

Difference between parallel and standard form pid controller in simulink?

What is the difference between parallel and standard form of pid controller that is provided by pidtool in Matlab simulink? In terms of block diagram?
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1answer
47 views

Syntax of complex numbers [closed]

In inductive reactance equation \$X_L = j2\pi fL\$, why do we write "j" in front of "2πfL"? Does it matter where we put it? Could you show me example where denoting real and imaginary number makes ...
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2answers
76 views

Matlab code to derive the overall difference equation relating two systems

Using Matlab, I am trying to: Get the overall difference equation relating to z[n] to x[n] and check if z[n] = x[n] is a valid solution to the overall difference equation I have two signals given ...
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2answers
57 views

Evaluating a logic circuit expression

My test says the answer is c) A OR B. To me it looks like: Q = AB + (A+B) What am I doing wrong? Which of the following is a logical expression that is equivalent to the logic circuit shown ...
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1answer
85 views

Differential equation for a notch filter RLC circuit

I'm trying to write and solve a differential equation for this simple RLC notch filter and I'm not sure what I'm doing wrong. simulate this circuit – Schematic created using CircuitLab So ...
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2answers
90 views

3 Resistor Voltage Divider Formula

I'm trying to analyze this circuit and spend almost 2 days to make a formula for it but I don't get it , anyone know what it's called or how can I make formula for it ? I want to calculate I1,I2,I3 ...
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1answer
118 views

Maxwell Equations for modeling a DC Motor

I have seen so many videos about this and none helped me. I can't calculate B. (equation:\$ E = 2*N*area*B*cos(\theta))\$. I mean... when I calculate the field B, I find high values for the current. ...
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2answers
74 views

Ultracapacitor, capacitance higher than rated?

Broadening my knowledge and experience about ultracapacitors I've made a test bench that was described in here. I've used an IEC methodology to calculate the capacitance: $$ C = (I_d*t_d) / (\Delta U) ...
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4answers
2k views

Mathematically modelling RC circuit with a linear input

I have found a plenty of documents and books that model how the voltage across a capacitor behaves within a transient RC circuit, using the following equation: $$V_C=V_{MAX}(1-e^{-t/RC})$$ ...
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28 views

What is T_e in stepper motor equation?

The description for T_e is missing on this page. Source: https://se.mathworks.com/help/physmod/sps/ref/steppermotor.html
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1answer
47 views

expressing a boolean function in another way

The following boolean expression is given: g(p,q,r) = ((p->q') -> r) Depict this boolean function only by using the operations ∧ (AND), v (OR), ¬ (NEGATION). How can I do this? I thought I could ...
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1answer
68 views

How to write inductor ODE equation properly?

I've drawn a following scheme, and now want to write ODE system for describing inner processes, in order to explore it: simulate this circuit – Schematic created using CircuitLab I wrote the ...
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1answer
332 views

LTSpice “Unknown parameter ”\“”

I am trying to simulate an electrical model (Mason Model) of piezoelectric system in LTSpice. So, I use parameters and formulas to evaluate the value of the passive elements in my circuit. I use the ...
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2answers
72 views

I need an equation to calculate the time for a power percentage of a half cycle sine wave into a resistive load

I need to calculate the time a thyristor/triac needs to be on for a desired percentage of full power of each half cycle of the AC line input. On for the full half cycle will give me 100%. On for 1/2 ...
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2answers
142 views

Differential equation of an OP AMP circuit with RC elements

I have to find the differential equation which describes the relation between input and output voltage for the circuit below. Per how the RC components are arranged, I simply can not find a ...
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46 views

Calculate U(t) when capacitor C1 charges C2 via a resistor R

simulate this circuit – Schematic created using CircuitLab The switch SW1 is activated at t=10s and charge from C1 is transferred to C2. The power supply charges continuously with 1kV 1mA. How ...
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0answers
92 views

Amplification equation for AC coupled Common Emitter stages

Do anyone can tell me how to get amplification equation for this circuit of coupled common emitter amplifier? simulate this circuit – Schematic created using CircuitLab Edit 1 Equation for ...
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0answers
41 views

Switched circuit analysis - getting rid of “glue” equations

I have the following circuit: simulate this circuit – Schematic created using CircuitLab I would like to derive 3 differential equations, describing it, since it has 3 dynamic components [Csh, ...
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0answers
306 views

Zener diode equation proof (chacteristic curve)

I'm trying to prove this equation(at least I think that's the correct one): which produces this graph: I can prove the one that describes the PN diode but I am not sure what I should do differenly ...
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1answer
53 views

Inverse Z-transform Problem [closed]

I'm rather stuck trying to compute the inverse Z-transform y[n] of the function below. I'm having trouble selecting the correct formulas from the table to achieve the right solution. Any help with ...
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1answer
76 views

WolframAlpha results for logic statement input

I was trying to simplify the following Boolean logic equation using wolframalpha.com. (not (A) and B and C) or (A and (not(B)) and C) or (A and B and not (C)) or (A and B and C) When I entered it ...
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1answer
61 views

Finding the unknowns of a current equation leads to non-sense

Suppose a series RLC circuit that is critically damped. Circuit is RLC in series with a DC voltage source \$ V_S \$ and a switch initially open. Capacitor and inductor are both discharged. at t=0 ...
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1answer
68 views

Trying to understand the magic the author of this PDF did explaining the critically damped equation

I am reading this doc about the equations for the step function for the RLC circuit, critically damped solution. At page 16 we have these lines... But there is a magic between these lines... How ...
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2answers
85 views

Trying to understand why the constant of integration was ignored on this RC circuit

I am watching this video where the guy deducts the voltage across the capacitor during the transient phase. There is an integral, in the middle of the equations. The guy integrates that and there is ...
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1answer
60 views

Trying to understand the transient current equation on a RLC circuit

I am reading this doc I see this magic happening on the third line of equations... How in the name of Math, does this \$ Ae^{st} \$ appeared there? Magic?