Questions tagged [electrical-engineering]

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33
votes
3answers
164k views

Why do we use Root Mean Square (RMS) values when talking about AC voltage

What makes it a good idea to use RMS rather than peak values of current and voltage when we talk about or compute with AC signals.
10
votes
5answers
21k views

Resistor circuit that isn't parallel or series

What's the equivalent resistance in this circuit (between points A and B)?
27
votes
8answers
108k views

Difference between live and neutral wires

In domestic electrical circuits, there are 3 wires - live, earth and neutral. What is the difference between the live and neutral wires? As there is AC supply, it means that there are no fixed ...
10
votes
6answers
21k views

What would be the effective resistance of the ladder of resistors having n steps

I'm a tutor. This is a high school level problem. In high school, every one have might have solved a problem of effective resistance of a ladder of resistors having infinite steps. Now the problem is ...
43
votes
3answers
40k views

Why do we use AC for long distance transmission?

Why do we use AC (Alternating Current) for long distance transmission of electrical power? I know that AC is such a current that changes polarity (magnitude and direction) and has fixed poles.
2
votes
2answers
23k views

How does current flow from the emitter, through the base and to the collector in a NPN transistor?

So, I understand that for a NPN transistor to work the emitter-base junction needs to be forward biased and the collector-base junction needs to be reverse biased. I understand how current flows from ...
0
votes
1answer
14k views

Equivalent resistance of unbalanced Wheatstone Bridge [duplicate]

Equivalent resistance of a balanced Wheatstone Bridge is pretty simple: if the corresponding ratios are equal the just cancel the wire connecting the centre of two wires. But what if they are not ...
4
votes
1answer
46k views

What is the role of center-tapping in a full wave rectifier?

Note: I have already tried googling. Although similar questions have been asked on different forums, I couldn't find a detailed explanation, which I could really understand. Circuit diagram courtesy ...
4
votes
2answers
613 views

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 ...
2
votes
1answer
817 views

Electrical flow in a simple parallel circuit

I'm having trouble understanding something in one of my text books: Let’s have a look at the implications of each circuit configuration. Figure 3.13 shows the Conventional representation of a ...
2
votes
0answers
183 views

Estimating the battery capacity using current power consumption and battery percentage

I want to estimate the current maximum capacity (in kWh) having the current power consumption (in kWh) and the state of charge of the battery (in %) available in a time series. I do not have a full ...
1
vote
1answer
649 views

Are quantum computers electronic?

I understand how normal logic gates operate and are implemented using digital circuits and electronics but I wad wondering how qubits are physically implemented. In other words is a physical qubit a ...
1
vote
4answers
5k views

Why should a voltmeter have a higher resistance than of any circuit element across which the voltmeter is connected?

According to my textbook, it is said that, for an ammeter: It is essential that the resistance $R_A$ of the ammeter be very much smaller than other resistances in the circuit. Otherwise, the very ...
0
votes
1answer
81 views

Saturated BJT Transistors. V CE < V BE : AKA - Things that make you go “Hmmmm”

At the risk of being blasted for cross-posting, I am posting this question again here in the Physics department. It is a duplicate of this post in the EE forum. However, I would like to get some ...
56
votes
3answers
9k views

Is there a physical limit to data transfer rate?

Is there a physical limit to data transfer rate (e.g. for USB $3.0$, this rate can be a few Gbit per second)? I am wondering if there is a physical law giving a fundamental limit to data transfer rate,...
16
votes
2answers
38k views

Why is Near Field Communication (NFC) range limited to about 20cm?

Near Field Communication (NFC) operates at 13.56 MHz. Near Field is the region situated at a distance r << λ λ = c/f ...
17
votes
2answers
8k views

Why don't they use springs as an energy source for cell phones?

I know they used springs for clocks way back in the day and now it's all lithium ion batteries. For reference, consider the Iphone that has a battery with a capacity of 5 Watt hours (18,000 joules). ...
4
votes
5answers
23k views

Current through the reverse biased junction in transistor [closed]

A transistor is a three terminal device. One terminal is called emitter, one collector and in between them is base. Now, during biasing the junction between emitter and base is made forward biased and ...
9
votes
3answers
4k views

Can a television detector van REALLY tell if you have the TV switched on? [closed]

In the UK, it was regularly advertised by the BBC, and the Post Office, that they had vans that could check if your TV was on, even if you were in an apartment block full of other people's TVS. TV "...
5
votes
6answers
20k views

Current when resistance is 0

A short circuit has $\rm 0$ resistance. We use Ohm's Law $\rm V=IR$. If $\rm R=0$, then $\rm V=0$. Doesn't this mean $\rm I$ can theoretically be anything? Thus $\rm I$ can be like $\rm35A$ for ...
4
votes
2answers
4k views

Strategies against 50 Hz mains hum on detector signals?

I'm having problems with a strong 50 Hz mains hum on signals created by photodetectors. I assume that they are due to ground loops and I realize that the best option would be to remove those. What are ...
1
vote
2answers
154 views

In the electrical circuit/fluid analogy is there an analogy for power loss across a fluid resistance?

For the fundamental passive $RLC$ electrical circuit, analogies are often used to describe the physics of fluid flow where $L$ represents the inertance analogous to inductance, $C$ is compliance ...
4
votes
0answers
664 views

Building a Faraday cage for mobile networks that is transparent for optical wavelenghts

A friend of mine is working on an architectonic project, where she designs a Faraday cage type of open space built in parks or other public places. The initial thought is to build it from some sort of ...
2
votes
2answers
199 views

How do you model the resistance across a symmetric sheet of plastic, streched (think ceran wrap) between a circular anode and cathode?

Here is the problem. You need to model the resistance across a circular sheet of polypropylene (plastic). The resistivity of polypropylene is 1E15 Ohms per meter. The expression for resistance on a ...
2
votes
1answer
139 views

What is energy band gap?

Explanations for graphene's high electrical conductivity often discuss energy band gap. What is energy band gap and how does it relate to the conductivity of a material?
2
votes
1answer
326 views

Memristors: how are memristors modeled in terms of impedance?

How are memristors modeled in terms of impedance? I have been searching the net for memristors, but could not get much of an idea. I'm not interested in how memristors are made (by combining ...
5
votes
2answers
543 views

Could we run an electric car on electric eels?

Could we run an electric car on a tank full of electric eels? I've heard electric eels are around 400 to 500 volts and can keep shocking for up to an hour. They also have a 10 volt system to sense ...
2
votes
2answers
2k views

Thevenin equivalent of a circuit

Ok so I can't post the image of my question and my attempt at it, so I would like to ask, if anyone knows the steps to simplifying a circuit with dependent current sources, independent voltage ...
2
votes
4answers
9k views

When does Thevenin's theorem not apply (modelling a power source with a ohmic internal resistance)

Most physics text books say that a power source can be modelled as an EMF with a internal resistance. This is also know as Thevenin's theorem or Norton's theorem. However I have read in some sources ...
0
votes
1answer
51 views

Resistance of a Large (relative to lead contact) Conductor

How do I calculate the effective resistance of a large piece of metal between two small electrical contacts? The thermal image (from an interesting but unrelated article called An Exception to Ohm's ...
0
votes
1answer
120 views

What is time badwidth product for pulses with GDD?

For a gaussian pulse the time bandwidth product is dwdt = 0.4. What is the time-bandwidth product for chirped pulse with group delay dispersion (GDD) added only ?
-5
votes
1answer
358 views

traditional transformer design improvement [closed]

The traditional tranformers suffer a lot of losses in various forms, some of them are as follows : 1. Flux leakage 2. Eddy currents 3. Hysteresis Figure : But as we are taught induction we come ...