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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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1answer
66 views

voltage potential energy clearance?

1 coulomb = charge of 6241509074460762607.776 protons(fixed amount of energy passing thru certain point). So 1 volt = 1 joule(energy) per 1 coulomb. and 2 volts = 2 joule(energy) per 1 coulomb. does ...
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1answer
44 views

Bidirectional level translator using N channel MOSFET

I'm using a n channel MOSFETa bidirectional level translator. The case when the body diode conducts the source end will be literally 0V or forward voltage of body diode, so the difference in voltage ...
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0answers
49 views

what is relation between Electric field intensity (E), Electric flux (Ψ) and Electric flux density (D)

As we know: Ψ = ∫E.dS By Gauss's law Ψ = ∮E.dS = Q / ε ε = permittivity of material inside Gaussian surface Q = enclosed charge in the Gaussian surface Ψ = total electric flux passing through ...
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52 views

Photons of RF energy [migrated]

So I start with the understanding that light is photons of electromagnetic energy, and that as the color gets more red the wavelength increases, and that an optical photon has both an electric and a ...
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1answer
90 views

Is it logically explainable that current is lower when torque higher?

I am modelling a motor with a little simulation script. The principle is: Input is the traction force needed to be provided by the motor Output is the current to be provided to the coil of the motor (...
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36 views

Schottky diodes operation

As far as I know the depletion region is created due to the diffusion of majority charge carriers which expose the charge of their ions. Is this the same for Schottky diodes (electrons diffuse from ...
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2answers
85 views

How does the arc extinguisher work in a miniature circuit breaker?

In a miniature circuit breaker, as shown below, the distance between open contacts is much less than the distance between metal bars in the arc extinguisher part (the gap gets progressively longer ...
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0answers
50 views

Magnetic locks with paramagnetic materials

Well I was wondering why magnetic locks are made of an electromagnet and a ferromagnetic material and not an electromagnet and a paramagnetic material. The magnetic attraction between the ...
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5answers
83 views

Why is Frequency Conversion Additive in Acoustics Beating, but Multiplicative in Heterodyning?

In radio electronics, one of the first concept to learn is frequency conversion by using a mixer. And it's strongly emphasized that the mixer is a multiplier, not an adder used in audio circuitry. The ...
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1answer
69 views

Magnetic force and Coulomb force

Lets have 2 electrons travelling with some speed relative to a static observer. The force between those 2 electrons will be the Coulomb force and the magnetic force. Is it forbidden from the laws of ...
2
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1answer
50 views

Mechanical Circuit Analog Question

I'm doing a practice problem from https://6002.catsoop.org/F19/ex11/mechanical_analog The problem is as follows: A mass m = 10 kg is at rest on a horizontal plane with viscous friction coefficient B =...
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2answers
58 views

Magnetic force as a function of PWM frequency

Consider an experiement with a DC source feeding an coil with a constant DC current I. The coil with an iron core attracts a magnetic plate with mass m with force F. The force F is higher than Fm and ...
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1answer
98 views

Slayer exciter(Mini Tesla Coil) Not Working[IRFZ44N]

I made a tesla coil as https://www.youtube.com/watch?v=Ca2e3evwVK0 's circuit. the MOSFET seems to be getting hot and current passes through the primary but I get no response from the secondary. ...
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2answers
51 views

How to find the voltage of a capacitor in a Op-amp + RC network?

I found this practice problem online which asked to find the voltage across the capacitor as a function of time. The circuit is: My intended approach is to first find the initial condition when the ...
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1answer
73 views

Deep explanation on TVS diode voltage suppression?

I am looking for a deep explanation on why a TVS diode suppresses voltage. All of the research I have done on Google just says 'it suppresses voltage by shunting current', but this doesn't make sense ...
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1answer
46 views

Network Identification - How to find R1 and R2

I've been working on this practice problem I found online. So, from the graph I understand that \$R_{eq} = 2000\$ for the entire circuit. Since I want to find \$R_1\$ and \$R_2\$. To do this, I turn ...
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1answer
56 views

Would a battery be considered an independent or dependent voltage source?

This is a very trivial question in my opinion, but I was thinking about what a battery would be classified as. In the physics world, batteries are often used to represent a voltage source. I feel ...
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1answer
44 views

Isolated circuits: can their reference voltages (GNDs) be at the same potential?

Suppose there are two independent circuits isolated from each other. If they are isolated, the impedance is very high between them (ideally infinite) and there is no current flowing from one to the ...
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3answers
184 views

Why does a Peltier cooler heat up when cooled by ice?

On this post, the question presents a problem of a Peltier cooler heating up after operating for a while. The explanation was that the Peltier cooler is only able to maintain a fixed temperature ...
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1answer
67 views

Contact potential between metals

Metals Al and Au are connected in series. An ideal voltmeter, with both of its leads made of Cu, is connected across them. Then how come the voltmeter gives zero reading but why can't we measure ...
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1answer
90 views

How do LEDs stay on constantly?

In a LED (light emitting diode,) a forward bias allows electrons to fill the vacancies in the p-type region, recombining with holes to emit a certain frequency of light. After a set amount of ...
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3answers
99 views

What happens to a computer as it is cooled towards absolute zero?

What happens to the behavior of a conventional circuit using conventional components as it is cooled towards absolute zero? To make this question more relatable: What would happen as we cool a modern ...
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4answers
424 views

How do thermal tapes transfer heat despite their low thermal conductivity?

I found myself needing to attach small heatsinks to Mosfets and CC power regulators. Also some high-power diodes. Today I have learnt that thermal compounds, even best in the market, are dozens of ...
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0answers
89 views

Ordinary LED response to nanosecond pulses

Can anybody explain to me the output waveform generated on pins of an ordinary LED when it is exposed to very short light pulses? I can clearly see that there is a precise difference in the length of ...
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1answer
79 views

Does these terms consider the same Voltage, electric potential, and potential difference

What are the differences between these terms ? do they are considered the same
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0answers
79 views

Switch to use in high g-force environment?

I need an on/off type switch (spst) on a device that will be subject to high, continuous centrifugal force loads (500-1000G or 5000-10000 m/s2)). Will your everyday, off-the-shelf switch handle this? ...
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1answer
73 views

Why do you have to bombard the inside of a neon tube to clean out any impurities? [closed]

Please include any website links that answer this question.
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2answers
65 views

Input capacitor of an amplifier

This one is very simple but I guess I am missing out something and hence finding it hard to understand. When a coupling capacitor is connected in an amplifier circuit, one of its plates is connected ...
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0answers
32 views

Realistic channel noise patterns

I'm setting up a playful coding challenge for our programmers. It's about coding theory. There are source, channel and sink. The task will be to implement an encoder for the source and a decoder for ...
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1answer
438 views

Is there any relationship between frequency of signal and distance it travels?

I'm currently researching 5G technology. Many videos/articles on this topic claim that 5G is designed for communicating on lower distances (than 4G), because of higher (than 4G) frequency. So to build ...
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0answers
73 views

Repurposing or obtaining a cheap audio signal amplifier for school physics lab

I teach highschool physics, and want to connect my smartphone (LG V20) to a Chladni plate (vibrating plate for studying interference patterns in sound in solids). I have successfully done this by ...
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1answer
105 views

Physical intepretation of the absolute value of impedance [duplicate]

If \$\rm{Re}( Z)\$ gives the reactance of a circuit, then what is the physical meaning of \$|Z|\$? How do they differ, and when would one use one over the other? (Where \$Z\$ is the impedance of an ...
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1answer
40 views

Electrostatics/conservation of charge

Conservation of Charge states that "Charge cannot be created neither be destroyed." If something cannot be created, then how it is in existence?
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1answer
51 views

Optimal Grounding for a PVC Dust Collection System?

It is common in woodworking (A hobby of mine) to make a dust collection system (Basically a tube hooked up to a vacuum to carry away dust created from automatic woodworking tools) out of PVC. We'll ...
1
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3answers
104 views

Is there a way to experimentally separate the effects of gate voltage?

I'm currently doing experiments on new kind of semiconductors. These devices have a body (source, drain) and a top gate. These devices show a response to gate voltage. The conductance changes with ...
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2answers
126 views

For an Ideal transformer where permeability of the iron is infinity, why is the excitation current 0 if the secondary winding is open circuit?

I have read this question Why is the Exciting Current zero in an ideal transformer?. However I don't quite understand where his initial equation for the excitation current came from. Can someone guide ...
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3answers
379 views

Homemade Faraday Cage?

I'm working in an office with a Wi-Fi router, desktop, and a few cell phones making RF noise. I have an 8 feet long by a 3-feet wide table, and I have an Aaronia BICOLOG 30100 + spectrum analyzer + ...
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0answers
57 views

If we're wearing a metal watch, do we get an electric shock on our wrist when we're charged and touch a conductor?

Or if the conductor itself is charged. As the charge would flow to/from the watch, assuming I'm insulated from the ground with rubber soles, or standing on glass.
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59 views

How to calculate the current produced by a solar panel?

The equation for calculating current when given voltage and temperature is known as the 5-Parameter model ie. \$I = I_{ph} - I_o[\exp(\frac{V + R_sI}{nV_t})-1] - (\frac{V+R_sI}{R_{sh}})\$ Since this ...
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3answers
170 views

Does voltage limit current?

When I short the negative and positive wires on my DC lab power supply, at ~1V the supply shows it's max current output of 5A. but when I turn down the voltage, at some point the output ampere ...
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1answer
54 views

MOSFET treshold voltage

Does anyone know how MOS treshold voltage varies if the physical distance between source and drain decreases ?
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3answers
250 views

Variable wavelength IR Diode?

I was thinking of building a DIY IR Spectroscope but for this, I need to find an IR diode that can do variable wavelengths. So far I have looked at Farnell and Mouser but all the diodes I have looked ...
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1answer
46 views

Explanation of 5 Parameter Model for Solar Cells

I am having a hard time understanding this equation, the 5 Parameter model for photovoltaic cells. \$I = I_{ph} - I_o[\exp(\frac{V + R_sI}{nV_t})-1] - (\frac{V+R_sI}{R_{sh}})\$ My goal is to apply a ...
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2answers
98 views

Three voltage sources circuit

Suppose the given circuit, find the current through the resistant R2 given that: E1 = 3 V E2 = 4 V E3 = 2 V R1 = 1 Ω R2 = 6 Ω I tried to apply kirchhoff laws but it was hard given such ...
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0answers
53 views

Why doesn't current leak to ground (DC)? [duplicate]

In the circuit shown below, I am considering ground to be ideal earth ground (stays at 0V no matter how much current it absorbs). It is my understanding that current flows when there is a potential ...
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3answers
773 views

How do electrons carry thermal energy in Peltier coolers?

I've read that when electrons enter from metal to semiconductor type N, they gain thermal energy and make that side cooler and the reverse happens when they leave semiconductor to the conductor. Why ...
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2answers
74 views

current speed/flow [closed]

Note my questions are in form of explaining. its because I've scattered information (or assumptions) and it want to link them. that's probably why you can see me explaining to much? Question part: ...
3
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1answer
129 views

Why are(n't) rechargeable batteries damaged by partial charging?

Over the years, I've come across websites and people with different opinions on the "correct" way to charge rechargeable batteries (I'm more concerned with laptop, tablet and phone batteries than with ...
2
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1answer
102 views

Estimate temperature for silicon (p-n junction)

I need to estimate the temperature at which p-n junction made of silicon lose it rectifying characteristics. (\$N_A=N_D=10^{15}\,cm^{-3}\$) \$E_G\$ is independent of the temperature and are 1.12 eV ...
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1answer
44 views

Non-Corrosive Water Sensing

I have been told that passing DC current through two probes in water will lead to corrosion on the terminals. Apparently AC does not cause corrosion. Preventing corrosion is of high importance to me....