Questions tagged [physics]
Physics is the natural science that involves the study of matter and its motion through space and time.
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Confusion about why pn junction discussion insensitive to doping variations faster than Debye length
Sze (Physics of Semiconductor Devices, 3e) gives the following discussion which relates to how equilibrium electric fields/equilibrium potential build-up at thermal equilibrium are related to doping ...
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How to derive the maximum power transfer theorem using the relation p=v²/R?
In most derivations of the Maximum power transfer theorem the derivation is done using the relation of power :
P = i²R
And on further derivation it comes out to be
Pmax = Vth²/4Rth
If I derive the ...
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Lightning board 3 meters
In France, you will see some signs like the one below:
Those signs are next to buildings which have lightning rods. They also have some conductors to make the current go from the rooftop to the earth ...
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Why don't oppositely charged ends of separate batteries and capacitors produce current flow? [duplicate]
I have a question here regarding the flow of current from charges.
I understand if you connect a simple circuit to a battery it creates surface charges which allow the current to flow.
My questions ...
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Thermodynamics of a simple electrical conductor
I derived an expression for the time constant of the temperature of an electrical conductor and was looking for some constructive feedback.
Initially there is no current flowing through the conductor ...
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Physics diagram to electrical schematic
After waiting a reasonable amount of time with no answer here, I have duplicated this question at Physics Stack Exchange.
I am asking this question on behalf of user furious.neutrino. This question ...
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Sizing MOSFET VDS to account for Stepper Back EMF
I'm having difficulty conceptualizing how the Back EMF of a motor, stepper in this case, can damage an H-Bridge MOSFET if the Vds aren't sized correctly. My main issue is my understanding of how the ...
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Seebeck Voltage [closed]
I understand that the voltage of two metal elements is V=(Sb-Sa)(T2-T1) regarding a thermocouple. But, what if mass was introduced to find the voltage? Can mass also be used to find voltage with ...
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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 ...
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Understanding the formula of the saturation current in a PN-junction diode
According to Wikipedia, the saturation current in a diode is given by the following formula:
$$I_S = qAn_i^2\left(\frac{1}{N_D}\sqrt{\frac{D_p}{\tau_p}} + \frac{1}{N_A}\sqrt{\frac{D_n}{\tau_n}}\right)$...
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What does it mean that an integrator has an infinite DC gain?
I mean, I get that, in the ideal case, \$G\rightarrow \infty \text{ as } s \rightarrow 0\$, but it doesn't make sense for a physical device to be able to amplify a signal to an arbitrarily large value,...
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How to find gain parameter of complementary filter algorithm for application in navigation
I am using mpu-6050 6 axis Inertial measurement Unit for navigational purpose for tracking orientation and position of a vehicle w.r.t starting point, I am trying to improve the orientation tracking ...
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How does electricity flow if circuit is not complete? [closed]
https://youtu.be/oI_X2cMHNe0
What is he saying at 13:20? How can bulb glow if the circuit is not complete?
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What is happening at the end of this circuit? Why is the voltage zero at the bottom?
What is happening to the voltage at the bottom? Why is it zero? How does the voltage go back to the positive terminal?
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Fundamental Question - how does magnetic permeability work for weak signals?
This is basically a physics question. If a sophisticated answer is needed, please go for it.
The standard explanation of magnetic permeability is something like this:
In a ferromagnetic material, ...
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What is the relation between the minority charge profile in the base and the collector current (BJT)?
For a BJT in forward active mode, the minority charge concentration at the base-collector junction is zero. If this is the case, how is a non-zero number of electrons able to make it to the collector? ...
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What goes on inside the transistor that amplifies the signal?
I understand that, for example, in BJT NPN transistor in common emitter configuration used as amplifier, feeding the small signal at the base will produce the larger signal at the collector.
But what ...
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Igniting and maintaining plasma in low pressure chamber
I'm trying to create and maintain plasma inside a vacuum chamber (up to 50 Pa), I have a home-made feedthrough done with an HV BNC sealed with Viton gaskets on a KF50 flange (makes a ≈25 mm gap).
I ...
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Do MEMS or optical gyroscope record Earth's rotational and revolutional angular velocities?
I am using a 3 axis gyroscope (Android device) to record angular velocities using a sensor data logger application.
When the device is placed stationary, the gyroscope recorded the following values:
...
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Construction of a Lagrangian function for a circuit
I was reading the paper "Introduction to quantum electromagnetic circuits", by U. Vool and M. Devoret and I am stuck in the construction of a Lagrangian function for the example LC circuit ...
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Equation for diode saturation current in photovoltaic cell model
I've been looking for mathematical models for photovoltaic cells. Most of the references I've found use the following circuit to the model the behavior:
Particularly, the diode current is modeled ...
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What is equilibrium carrier concentration in a semiconductor? Is it material specific? How to calculate it?
Is equilibrium carrier concentration dependent on doping density? If it is, then how to know how much the doping density should be for a particular semiconductor device?
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How does the electric field inside a conductor remain zero?
I'm learning about current in conductors, and came across the statement that "The electric field inside a perfect conductor is zero", this is frequently explained used Gauss´s Law by saying ...
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Why do we use silicon in the crystal direction [1 0 0]?
In MOSFET, we use silicon in crystal direction [1 0 0] , while we use direction [1 1 1] in BJT. What is the reason? I expect the opposite, because we see more atoms on the surface in the direction [1 ...
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Why don't we consider drain-bulk voltage instead of source-bulk voltage in body effect?
Why don't we consider drain-bulk voltage instead of source-bulk voltage in body effect?
For example, in the threshold voltage formula, we have source-bulk voltage, not drain-bulk voltage.
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How does a electrical device draw its rated current?
I am learning electronics and this question has been bugging me quite a bit. If I have a device, let us say rated at 6 volts and 350 mA, this means the device will work when there is a potential ...
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How do I calculate threshold voltage from the graph?
I have a table of values given to me which contains drain current Id (in μA) and gate voltage (in volts) calculated in the saturation region for a thin film transistor.
I need to find the threshold ...
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Calculate complex impedance value from voltage in time domain waveform
I have problem. I was doing an electrochemical impedance spectroscopy (EIS) test on my Randles cell.
simulate this circuit – Schematic created using CircuitLab
The data from potensiostat's ...
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Difference between arsenic and phosphorus in IC fabrication technology
What is the difference between arsenic and phosphorus in IC fabrication technology? When do we prefer one of them over the other?
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Is birefringence exploited or otherwise meaningfully observed anywhere in electronics?
Birefringence is a property of certain materials where the refractive index of the material is dependent upon the polarization and direction of propagation of light through it. I recently learned ...
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Calculating steady-state temperature for electrically heated wire
I am working on a program aimed at finding optimal parameters (voltages and feed rates) for a hot wire foam cutter. One starting problem that has to be solved before even attempting to evaluate heat ...
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Why is the gamma term missing in the first case of single transistor example?
This is the video.
How is the gamma term present in one case and absent in another?
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Maximum weight for robot arm - MG996R [closed]
I want to build a robot arm (see here) to move a dumbbell of 2 kg (roughly 2.2 lbs).
However, since I have no background in engineering, I have no idea how to calculate / find out if the servos used (...
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Why does current flow direction matter in welding?
In DC welding, there are two configurations - direct current electrode positive (DCEP) and direct current electrode negative (DCEN). When the electrode is negative, the current flows from electrode to ...
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How can I calculate how long it will take equipment in an enclosure to overheat?
This is kind of a follow-up question about determining the heat dissipated from equipment based on power consumption.
I have a situation where I have to install a router and UPS system in an enclosed ...
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How to compute flux through a sphere when flux density is given in rectangular co-ordinates?
Compute the total flux of D leaving a sphere of radius 1m, and hence the total charge enclosed by that sphere. D(x,y,z) = xX̂
Attached is my current working and the worked solutions provided to us. ...
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Fermi level of metal
Do metals have fermi level? As we know conduction band and valence band are overlaped for a metal. Does it make any sense for metals to have fermi level?
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Is it possible to ignore Nyquist-Shannon theorem?
I have a case in which I have to find a frequency of wavering object with camera (some kind of visual odometry). There is a limitation: frequency of a filming camera (fps) should be at least twice ...
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Why do we subtract horizontal and vertical component of a electric field?
I was solving a question of electrostatic which is: Find the electric field at a distance z above one end of a straight line segment of length L that carries a uniform line large lambda.
My question ...
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Thermionic emission
I am doing the calculation for the "finding the temperature of filament".
I tried with:
Resistance (R=V/I)
Resistivity (ρ = R·L/A)
Temperature (T = (ρ-ρ0/ρ0-δ) + T0)
Here ρ0, δ and T0 are ...
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Can't find error in nodal analysis
For the following circuit I did node analysis in order to find the greatest possible power at R and ended up with the equations (using node analysis):
$$n_1:\frac{v_1-V}{R_1} + \frac{v_1}{R_2} = 0$$
$$...
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RGB LED Color Calibration to D65
I am trying to determine resistor values to set the forward current per color of an RGB LED.
I would like to achieve approximate D65 (daylight white) when all LED channels are driven at maximum ...
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How to calculate total power required for an electric vehicle (ebike) design?
I wanted to design an ebike with good enough specs to satisfy my requirements, my first consideration was the power required to move the bike at my required speed and from there I can choose a motor.
...
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Transmission Line model [closed]
Can some one explain me why exactly classical circuit theory fails to account for the wave nature of EM fields and how the transmission line model accounts for it better
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Why don't (military-grade) parts provide g(acceleration) metrics? [closed]
What is the maximum acceleration a device can handle which is capable of:
GPS
RF communication up to several of kilometers
visible and/or IR cameras
(basic) radar?
This thread insists "over ...
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Does the direction of coil winding impact the direction of induced voltage?
I have taken and modified a bit the following image from a similar question, where it was explained that the direction of the coil winding does not impact the direction of the current: Does coil ...
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Is it possible to force charges into one plate of a capacitor?
As we know, a capacitor stores energy, but the net amount of charge in it doesn't change. If an electron enters one plate, another leaves the other plate. If the other plate is floating, the entering ...
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Trouble with body effect physics
I’m struggling to understand why a negative voltage applied to the bulk contact of an n-type MOSFET increases the threshold voltage.
I read other similar questions and I get that the negative voltage ...
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GaN Vs IGBT performances
I was making some research on GaN and I do not understand why GaN is so reveolutionnary. When I take a look on the following specification RdsOn and Coss (Cds + Cgd), the GaN semiconductor has lower ...
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Calculation of series circuit elements
I have a series circuit. Should it be true for this series circuit if I true to write like:
...
