Questions tagged [equation]

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The probability that an electron occupies the fermi level at 0K

I was trying to find the probability that an electron occupies the Fermi level at 0K. Fermi function: {exp[(E-Ef)/kT] + 1}-1; (k = 8.314 J/mol/K) According to my calculations, the answer would be 0.5. ...
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1answer
92 views

Any short formula for PCB trace capacitance when w/h <<1 [closed]

I have this formula/equation e(w/d) for capacitance of PCB traces (parallel plate). But as it appears, this equation is valid for the assumption w/d>>1 (much greater). And multiplying 11.3 with ...
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3answers
117 views

Finding the current through an inductor in a second order circuit?

Assume that the circuit has reached a steady state. I'm trying to find the current through the inductor at some time, t, which should be a function of t. I'm having trouble creating a system of ...
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1answer
91 views

Calculating time constant of a less than 50 % duty cycle 555 timer circuit

I am building a 555 timer circuit that generates a pulse for my servo motor. The circuit in mind looks like this: I got this circuit from this site, and it uses a (1N4148) diode, -the same one I ...
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2answers
70 views

ohm's law and power equation

I have a question about electricity. I know that transmitting power over long distances is better in AC. I also heard that the voltage needs to be high to reduce losses. I want to calculate this for ...
-1
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2answers
101 views

Switching DC battery on ideal choke?

(Google translation). A switch is activated at the instant t = 0 in a series circuit containing a battery of voltage U (ideal) and an inductor L (ideal). I am in doubt with the answers I have found on ...
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2answers
100 views

Inverter Fourier analysis

I have an inverter circuit like below: I will use bipolar control method to produce sine wave. Our teacher said us prove basic harmonic of inverter is equal to multiplying of modulation index and Vd, ...
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2answers
69 views

In parallel current sources with capacitors

I have to get the correct equation of multiple parallel non-dependent current source in parallel with capacitors, as i seem to find the correct solution, the resulted simulation in LTSpice shows ...
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2answers
98 views

(Almost) Wheatstone bridge

I have this wheatstone bridge: Rmeasure is the impedance of my voltmeter between A and B. My goal is to have the equation of R1/R2. Because Umeasure changes if \$R_2\$ or \$R_1\$ changes. the values ...
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0answers
46 views

Is there software with CAS to solve drawn electrical circuit in form of differential equations which describes that electrical circuit?

Is there any software with Computer Algebra System to solve drawn electrical circuit in the form of differential equations which describe that electrical circuit? Or to write symbolic solution (...
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3answers
2k views

I think I found an error in an electronics book. Are my equations correct here?

I'm reading Practical Electronics for Inventors, 4th edition, to freshen up my long forgotten knowledge of electronics. I love the book so far, but I just came across an equation there which seems ...
2
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2answers
104 views

Confused on the notation from a TI datasheet

So I'm trying to implement this IC onto a controller that I'm designing: https://www.ti.com/product/UCC5350 I understand for the most part how to apply it, I am just lost on one key part The specific ...
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1answer
98 views

What equation should I use to calculate inductance of wire coil?

I've been working on a project recently which requires me to build an inductor, however in my research I found many different equations (with a range of variables used and giving very different ...
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0answers
38 views

BLDC motor equations

I've read this article about driving gimbal motors. I have some questions about these equations: I don't understand what "ψ" and "Lω" means and generally i don't understand how to ...
2
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1answer
96 views

RC Circuit Equation

I am a beginner electronics hobbyist. I found this book called Basic Electronics for Scientists and Engineers and I am currently reading on RC circuits but got stuck trying to understand the equation. ...
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1answer
63 views

Differential equation of the NPN transistor configured as a voltage divider

The mathematical model in AC of the NPN transistor is represented by the pi model which is only one resistance in parallel to the resistors of the divider and the DC source in parallel to the ...
1
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1answer
128 views

MOSFET operating point in linear mode

I have this question, where the drain-source current and its bias gate voltage of a MOSFET is known where source is connected to ground. I find its drain current is less than saturation current by a ...
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1answer
883 views

simulating equations in LTSPICE

I have a dependent current source which depends on external pressure given by quadratic equation. Is it possible to simulate it in LTspice and see the graph between voltage or current and pressure?
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0answers
53 views

Is mmf the same as the magnetic force?

In the following system, I created the following equation in terms of what I assumed to be the force acting on the movable object with a mass M. The reluctance of the core is neglected, so the total ...
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0answers
77 views

How to model Nernst equation for numeric solution?

I want to write a program (this is not programming question!!) that numerically solves voltage across virtual battery-resistor circuit over time. But sometimes explanations is too overcomplicated, not ...
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1answer
65 views

Equations in electrical circuits

This might be more of a math question but when solving electrical circuit problems, if f(x-1)= x What is f(x)?
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1answer
257 views

Equation to calculate voltage divider resistor value for an input of op-amp

I found this guide for a temperature sensing circuit design with NTC thermistor by Texas Instruments. According to my opinion, optimum R1 value is calculated so that the voltage divider can provide ...
0
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2answers
54 views

How does Impedance matching equation work out from original link?

From this link: L-Pad Impedance Matching Equation How do you get those two equations? They do not look like a voltage divider formula, do they? Questions repeated here: First answer from Adil ...
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2answers
62 views

What is the theory behind these current equations? (for Z paramaters)

In the photo below is shown the method for deriving z-parameters of the circuit. Apologies for my badly drawn values for resistors as they weren't shown in the original image. Basically I'm struggling ...
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1answer
183 views

Deriving the Impedance equation of a RLC circuit (with 2 Inductor)

simulate this circuit – Schematic created using CircuitLab During this lockdown I had some time in hand and decided to learn more about impedance. So I gave myself a project, trying to create a ...
2
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3answers
516 views

Finding equation of curve for NTC type thermistor [closed]

I have an NTC thermistor from the KTM 390 engine which I am trying to interface with the Arduino MEGA. The problem is the sensor has no datasheet. I have got the relation between the temperature vs ...
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0answers
90 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
75 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
522 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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0answers
31 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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1answer
434 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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2answers
675 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
192 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
76 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
214 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
298 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
235 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
97 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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0answers
33 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
49 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
75 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
2k 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 ...
2
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2answers
139 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 ...
2
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2answers
493 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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0answers
53 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
163 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
980 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 ...
0
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1answer
63 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 ...