Tagged Questions

An electronic system, with closed loop current flow, and relative electrical potentials present across electrical components.

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2
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1answer
853 views

How is contact resistivity defined for a Schottky contact, or the Schottky barrier height for an ohmic contact?

Based on the transfer length method (TLM), one can accurately calculate the contact resistivity for an ohmic contact, by evaluating the absolute resistance measured through the test structure and ...
4
votes
2answers
2k 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 ...
7
votes
4answers
5k views

Resistor circuit that isn't parallel or series

What's the equivalent resistance in this circuit (between points A and B)?
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vote
1answer
2k views

RC Circuit , Calculate Time Constant

Given this diagram: With S1 switch closed and S2 switch left open, I am trying to find the time constant Relevant equations I know τ = RC for a basic circuit, but how would you calculate it for a ...
-2
votes
1answer
402 views

what is the proper way to connect two light bulbs in a circuit? in series or parallel?

What is the proper way to connect two light bulbs in a circuit? in series or in parallel and why? My thought is that it's better to hook them in parallel, since if we take into account Ohm's Law, the ...
4
votes
1answer
1k views

General integral to find resistance

My question is: is there a simple and truly general equation for the resistance between two electrical equipotential surfaces?. Obviously, if so, what is it, and if not, why? It would be very ...
4
votes
1answer
591 views

Turn-on delay time for Laser diode

Do you know any simple explanation on the reason why the turn-on delay time on a laser diode is reducing while we increase the bias current? Turn on delay,is the time that the laser needs from the ...
1
vote
1answer
1k views

How to calculate the charge and the potential across a charged capacitor charging an uncharged capacitor?

Initially, there is a single capacitor $A$ attached to a power source that charges it to a certain voltage $V$. Once it is charged, it is instantaneously removed and placed in a circuit with an ...
10
votes
3answers
483 views

Current in a simple circuit

I was going over my notes for an introductory course to electricity and magnetism and was intrigued by something I don't have an answer to. I remember my professor mentioning, to the best I can ...
1
vote
0answers
114 views

Simplifying a biquadratic filter equation [closed]

I am trying to calculate input impedance of a multiple feedback low pass filter. What I need is the symbolic expression as simple as possible so that later I fill in the values and get the impedance ...
3
votes
3answers
2k views

How much energy was consumed when we turn on/off light?

My parents told me to turn off the light when I am not using it. But I remember my physics teacher told me that the action of turning on/off a light can cause huge energy. I am wondering how much is ...
0
votes
1answer
1k views

As ISA Practical - Resistors in Parallel [duplicate]

Possible Duplicate: Current against the inverse of resistance graph, I = V/R +c How would you set up a circuit with a fixed resistor in parallel with a variable one. We are told to measure ...
2
votes
1answer
521 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 ...
3
votes
1answer
101 views

buiding circuits from color superconductors

caveat: the sort of exotic matter engineering in here is currently beyond the reach of our technology, but, that having been said: Has their been any research on building models of these sorts of ...
3
votes
2answers
2k views

Relating milliampere-hours to watt-hours for batteries

I've seen many batteries that are measured in milliampere hours (mAh), while others are measured in watt hours (wh). How can I convert them between each other so that I can actually compare them? It's ...
0
votes
2answers
3k views

Internal resistance V=IR circuit question [closed]

I don't know how to resolve this problem. A complete circuit consists of a 18,0 V battery (internal resistance r) and a resistor R. The terminal voltage of the circuit is 15,8 V and the current is ...
2
votes
1answer
302 views

What electric potential is found over individual resistors connected in series to an AC power supply?

Given a set of resistors connected in series to an AC power supply: What formula governs the peak-to-peak voltage which will be measured when voltage is probed over individual resistors and sets of ...
1
vote
1answer
4k views

Current against the inverse of resistance graph, $I = V/R +c$

If I have a plot of current ($y$ axis) against 1/Resistance ($x$ axis). The circuit it is measured from is a simply 2 resistors connected in parallel to battery, where the potential across the ...
3
votes
2answers
502 views

The role of resistor in e.g. an AND gate

What is the role of the resistor in e.g. an AND gate like this one? : One often sees lots of resistors in electric circuits, but I haven't really understood their role.
2
votes
2answers
3k views

Voltage and Current in transformers

In transformers, the ratio of the voltages equals the ratio of the turns - so double the output coil's turns and the output voltage doubles. Then, in order to conserve energy, current halves. This ...
2
votes
2answers
1k views

What is the potential difference between point X and point Y?

Here is the problem: In the above figure I want help on finding the potential difference between X and Y. It is getting quite confusing due to the battery in the middle. I found the current in both ...
7
votes
1answer
679 views

Can an arbitrary RLC-circuit network have non-minimum phase zeros?

I am working with certain input-output maps that can be thought of as large RLC-networks. I thought maybe this might be a place to get some thoughts/ideas/answers. My basic question is, given some ...
11
votes
8answers
10k views

What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)?

This is a confused part ever since I started learning electricity. What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)? All of them have ...
2
votes
1answer
284 views

Circuit Simulation

I am making a circuit simulation program, and I am not sure how to simulate the behavior of Diodes. Take this circuit: ...
7
votes
3answers
2k views

Tying knots in power cables to prevent power surge from lightning strikes

There are plenty of references to this claim on the internet that tying knots in power cables will prevent a piece of equipment e.g. television or computer from a power surge. How can this be ...
0
votes
2answers
1k views

Electric field of not-grounded conducting plate with a given potential?

I have been trying to find an equation (or some solution) of how to calculate the electric field strength (in N/C) of a conducting rectangular (nearly flat) plate which has non-zero potential to it, ...
0
votes
3answers
5k views

Calculating time for a fully charged UPS

I have a UPS of 1000 Volts connected with 2 batteries each of 150 Amp. How much time it will take to consume the whole UPS (after fully charged) when a device of 1Amp is getting electricity form that ...
2
votes
1answer
309 views

No Voltage in a Circuit but still a Current, How?

Hi I've done an experiment in physics using a basic circuit. Can anybody explain how come the data logging equipment I was using continued to register a current when there isn't a positvie voltage in ...
6
votes
6answers
9k 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 ...
2
votes
3answers
4k views

Wheatstone Bridge

Why is using a Wheatstone bridge such an accurate way of calculating an unknown resistance? What are the benefits of using it over Ohm's law? It seems that it has something to do with the wires ...
18
votes
2answers
2k views

The “Nerd Sniping” problem. Generalizations?

This question is motivated by this xkcd comic strip . The problem is indeed interesting, and my first recollection upon reading this was a similar problem in the book Problems in General Physics by ...
0
votes
1answer
212 views

Waveforms for a given ideal inverters circuit

I have the following circuit. All the inverters are ideal CMOS. I need to draw the waveforms for each point (A, B, D, E, Vo), given that waveform at input. What I want to ask is if what I did so ...
22
votes
4answers
4k views

Why do 'dead' batteries work again after exchanging the places of the batteries in an electronic device?

My camera, which is powered by two AA batteries in series, would not power on. I removed the batteries, exchanged their locations, and the device worked again - for another 15 minutes or so. The ...
2
votes
4answers
2k views

Calculating current used by individual resistor?

I just recently finished a test on Physics, and when receiving my scores back I missed a question. Here's what it was if I can remember it correctly: Three resistors (10.0, 15.0, and 6.00 ohms) ...
0
votes
1answer
3k views

Ohm's Law and Space-Charge Limited Current

I am trying to understand Space-Charge-Limited-Current (SCLC) and the resulting Mott-Gurney Law. My main problem is conceptual; I don't get why SCLC doesn't produce Ohm's law (j $\propto$ V).
6
votes
2answers
1k views

Lots of little questions about radiation of LC circuits

I'm trying to get a more intuitive understanding of resonant inductive coupling. It's supposed be a more efficient way to transfer electrical energy wirelessly, because the coils are only coupled by ...
0
votes
4answers
681 views

Voltage drop along an idealized resistance-free wire in a circuit?

If you connected the positive terminal of a battery to the negative terminal to a battery with a wire with (hypothetically) no resistance, and are asked to give the voltage drop of a segment of wire ...
3
votes
3answers
5k views

What is a virtual ground?

What is a virtual ground? I would like to know what it is.
9
votes
1answer
1k views

Matrix solution of an equivalent resistance circuit problem

Start with a set of points $x_1, x_2, \ldots$ that are connected by wires with some resistance. Represent the resistance by a conductance matrix (conductance being one over the resistance), where ...
0
votes
3answers
2k views

Direction of Magnetic force from a current running through a coil of wire

What is the direction is the magnetic force vectors pointing from a coil of wire that has current running through it? ...
-1
votes
1answer
638 views

How does mass relate to resistance (Ohm's Law)

How can I relate $mg$ to $R$? Just to give you a scenario: If a free hanging weight was tied to a motor... I know the voltage ($V$) and current ($I$) so I can use $V = IR$ to find $R$. What if I ...
5
votes
5answers
897 views

How long would it take for electricity to flow from one terminal to other, via a 1 LY long wire?

Basically, how long does it take for electricity to determine there is a closed circuit and how does it know that the circuit exists? I'm curious to know how it knows there is a closed circuit at any ...
11
votes
8answers
19k views

Electricity takes the path of least resistance?

Electricity takes the path of least resistance! Is this statement correct? If so, why is it the case? If there are two paths available, and one, for example, has a resistor, why would the ...
5
votes
3answers
8k views

What happens when we connect a metal wire between the 2 poles of a battery?

As I remembered, at the 2 poles of a battery, positive or negative electric charges are gathered. So there'll be electric field existing within the battery. This filed is neutralized by the chemical ...
49
votes
2answers
30k views

On this infinite grid of resistors, what's the equivalent resistance?

I searched and couldn't find it on the site, so here it is (quoted to the letter): On this infinite grid of ideal one-ohm resistors, what's the equivalent resistance between the two marked nodes? ...
7
votes
3answers
3k views

Is it safe to use any wireless device during a lightning storm?

I need "educated" reasons whether it is safe to use any wireless device during a lightning storm. Most people said don't use it but they cannot explain why.
2
votes
1answer
1k views

Current from induced emf

If the induced emf in a circuit is negative, and current from this emf is the emf over the resistance, what happens to the negative sign in the induced emf when solving for the current? Surely there's ...
6
votes
1answer
921 views

Why does breaking one bulb on a string of Christmas Lights cause all the rest to break in some lights?

If I break one bulb on a string of Christmas lights, or the filament goes out, then all of the rest seem to stop working. Why is this? However, I've also seen the opposite happen in some newer ...