# Tagged Questions

Electronics is the study of electric circuits and electrical components, and the design of useful devices. Some questions in this tag may be more appropriate for the [Electrical Engineering(http://electronics.stackexchange.com/) SE site.

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### Calculate amount of gas flowing in a pipe [on hold]

I have two tanks of a gas which are connected to two different pipes and supplied to two different furnaces. I need to keep a check as to what is the quantity of gas (in KG) that is consumed at any ...
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### Inside computer processors what physical phenomena represents a 1 or 0 [on hold]

I understand how transistors work as switches but am struggling to understand what is detected as the output that is know to be a one or zero. I aim to understand the link between the current flowing ...
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### What are the advantages of using a centre tapped transformer in a full wave rectifier? [on hold]

What can be the merits of using a centre tapped transformer in a full wave rectifier circuit? A half wave rectifier does not use these centre tapped transformer, still it does produce its output....
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### Can an electric circuit be modeled from tracking individual charge carriers?

Given a simple electric circuit , If we were to start from tracking all the forces acting on each individual free electron in the circuit, would it be possible to eventually find all the currents and ...
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### A logic question on binary variables

I recently purchased some nightlights with sensors. The sensor will make sure the nightlight will only be tuned on in a dark environment. Let's assume the sensor is binary, ON or OFF. Here is the ...
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### Capacitors in space [closed]

I'm new here and I have a question for all of you. What happens to a capacitor in open space? There are different kind of them, which one of these is better to use there? And... We know that if we ...
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### Won't the Power be dissipated in the first quadrant of this graph?

In the following picture: In the first quadrant of the V-I graph(for an Independent Current Source, where the voltage supplied is positive on the top) won't the power be dissipated instead of being ...
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### Which AC bridge circuits are oscillators? [migrated]

There are different types of AC bridge circuits like the Wheatstone bridge, Maxwell, Hay, Shering and Wien. I need to know which ones are oscillators but I still don't get the main reason why the ...
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### Which is better conductor silicon or germanium and why and also which has more band gap and why and what affects the band gap in material?

want to know on what factors energy band gap depends upon.as per me it is due to electron-proton attractive forces but according to this germanium should have higher gap than silicon but germanium has ...
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### holes in an electronic circuit [closed]

Many times, by looking at electronics circuits I noticed that they have like small holes printed in yhem. The question I want to ask is, what s the purpose of these holes?
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### Green LED Forward Voltage

Yesterday in lab, we were asked why all of our green LED had large forward voltage than expected. We expected for the forward voltage to be at around 2.1V as according to hf=Egap=eV. Yet, we ...
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### Can you get a better signal to noise ratio by connecting multiple microphones in series?

From my very basic understanding of microphones, they generate a tiny bit of electricity as the membrane moves, this is the signal. It would stand to reason then, that if I connect a bunch of ...
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### Video recording interference

I'm currently working on an Android App that records while driving in a car. Similar to the popular Dashcams. While developing this App I saw a lot of ugly glitches on my videos. I used a Nexus 5 for ...
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### Can we “use” a capacitor while simultaneously charging it?

I know that capacitors can be charged to work like a battery . But I wanted to know whether we can charge a capacitor while it is in use ( given that the current supplied to it is more than what it ...
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### Why is the satellite dish still needed?

How much does it amplify the signal? The receiver cannot pick up the signal without the dish? Is it possible that it will disappear in 10 years? As the sensitivity of the receiver is enhanced? ...
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### Electronics book for physics undergraduates

I am going through very hard time studying electronics, I studied little electronics at high school (what is diode, transistor, etc). Now in clg now I need electronics to study, I don't understand ...
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### Normalizing temperature data of CPU sensors to ambient

My scenario: I want my application to stop or take some decision based on temperature. say like if my ambient is morethan 41 i want to switch off the application and we do not have an separate ...
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### what is the effect of temperature on the resistance of a photoconductor?

As we know, for a photo conductor resistance tends to decrease with increase in irradiance, but with greater irradiance comes greater temperature. Also we know, photo conductors are semiconductors,...
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### Why is $np$ always equal to $n_i^2$?

For you guys who studied semiconductor physics must be familiar with the equation: $$np=n_i^2$$ I can understand why this is true for the intrinsic case (the broken bonds would always provide ...
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### Cds photoresistor cells [closed]

We understand (from Wiki) that when light hits the photoresistor cell, the resistance goes down, electricity flows more easily. But dont understand how resistance going down would work to turn OFF a ...
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### Reducing voltage with resisitors [closed]

I am working on a project in structure, in which i have to rotate the second storey of my building, now my assembly consists of 12 v battery connected in parallel with 12v motor which is connected to ...
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### Things that must be considered when mass producing a capacitor [closed]

The question is to list four things that must be considered when a capacitor is chosen for inclusion in a circuit which is to be mass produced. Are there a specific set of four things? I've come up ...
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### Specific heat capacity for solids of changing temperature

I was reading the following post: If the specific heat capacity depend upon the temperature, what formula we should use instead of $Q=mc\Delta T$ and I understand that the total energy needed is ...
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### Problem in resonant tunneling diode (RTD)

What happen if the two barrier width in RTD are not same? How the transmission coefficient change for this? How the dips are formed in the transmission coefficient graph?
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### Potential Difference Across Components in Parallel & Series Circuits

So I have two questions, but they're kind of linked so I'm putting them in one. 1) I have a simple circuit with a battery connected to three lamps in series. If I then add a second battery but ...
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### How would you read memristor data?

According to many experts; memristors have the potential to change and drastically improve data storage and processing power of computers. But there is one small thing that doesn't fully make sense to ...
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### What is the potential difference across a disconnected diode? [duplicate]

I think potential difference across disconnected diode should be zero but how? the last graph tells that there is a potential difference between the two ends of a diode. then how can be it zero?
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### The width of the space charge region in a pn-junction

Given a pn-junction as in the picture below. Which quantity determines the width of the space charge region? Or in other words, why don't the electrons in the n-doped region wander towards the ...
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### Equivalent DC circuit with charged conductors

I am trying to find equivalent circuit for a circuit composed of interconnected capacitors when isolated pieces of conductor may carry nonzero electric charge, and I have been struggling with this ...
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### Why does this magnet not damage electronics?

The "magic cellphone holder" found at this link works by taking advantage of a magnet and a metal plate that you stick to your phone. Why does the magnet not damage the electronic components of the ...
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### Can seebeck chips be used to extract Peltier chip waste heat?

I understand that a problem with employing the Peltier effect for the purpose of cooling is that it produces a significant amount of heat on the hot plate. But why don't we use seebeck optimised chips ...
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### Why is 2-terminal sensing less accurate than 4-terminal sensing if the internal resistance of leads is known?

I have a pretty good understanding of 2-terminal vs. 4-terminal (kelvin) sensing measurements. I understand that in the 4-terminal measurement, current is supplied by 2 terminals that are separate ...
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### How the voltage of a capacitor is changed in charging/discharging [closed]

Capacitors are called fast batteries in electronics. I understand that a battery is charged by a constant current while the voltage is almost constant during charging and discharging. For example, a ...
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### Electron jump into a transistor to read qubit state

Prof. Andrea Morello, a quantum physicist, in one of its quantum computer models uses the spin of the outermost electron in a phosphorus atom to represent a qubit. This atom is embedded to a transitor....
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### Thermistor is more sensitive than metals [closed]

Can anybody tell me, why a thermistor is much more sensitive at temperature variation than a metal?
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### Which law of physics is applicable for communication? [closed]

What is the physics behind communication like internet, mobile phones etc. What are the equations?
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### Charge in capacitor after switching voltage

Say you have a capacitor connected to a voltage source (vs). After the capacitor has fully charged, you cut the source voltage in half to vs/2. The voltage across the capacitor should change to match ...
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### How to control a dc motor? [closed]

I am in 8th standard and I am doing a project on 3d printing pens. I want to know how to control a dc motor, so that when I press a button it should increase its speed gradually till it reaches its ...
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### Why for each electron – hole recombination, an electron from the negative terminal of the battery is released

Why for each electron – hole recombination, an electron from the negative terminal of the battery enters the N-region and then drifts towards the junction?
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### Differences between Metal-Bridge-Metal system and Donor-Bridge-Acceptor system

What is the real difference between Metal-Bridge-Metal system and Donor-Bridge-Acceptor system? In MBM there are anchor groups between the molecule and the metal electrode, can’t the groups act as ...
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### Electron gun and oscilloscope

Aren't the electrons exhausted in the electron source of electron gun? And what is the fate of electrons that strike the sulphide coated screen to produce luminescence?
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### Why do electron emits energy in a LED when they transfer from the n type semiconductor to the p type semiconductor

after an electron moves from the n-type into the p-type silicon, it will combine with a hole and disappear. That makes an atom complete and more stable and it gives off a little burst of energy. But ...
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### What's the purpose of capacitors in parallel

In my school textbook it is written that the capacitor acts as a filter, that is, it decreases the fluctuations in the potential difference across the load. But since all the components are ...
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### Do oscilloscope have a lifetime? [closed]

The electron gun in an oscilloscope is, from what I understand, analogous to the one of a Cathode Ray tube. It is made of a material that emits electrons via thermionic emission. Doesn't this slowly ...
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### Why does the metal mesh in an electric swatter make a whirring sound?

I have an electric bug swatter that operates on a rechargeable lead acid battery. I had one before that operated on disposable batteries and when it was turned on, it made a high pitched whining noise....
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### why is I-V characteristics of a solar cell drawn in the 4th quadrant?

My book says because a solar cell does not draw current but supplies it to the load. I don't quite get the explanation. How is it related?
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### Semi conductors (holes and electrons)

The following relation is mentioned in my text book for semiconductors in thermal equilibrium. $$n_e ×n_h = n_i^2$$ $n_e$ stands for the number of electrons. $n_h$ stands for the number of holes. ...
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### Is it possible to make a capacitor of required specifications using aluminium foil? [closed]

I wanted to make a FM radio transmitter but I was not able to get a capacitor with the exact rating of certain micro farad and pF. But I live in a poor country and I can not find them in the local ...