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

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55
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2answers
37k 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? ...
43
votes
7answers
6k views

Cyclist's electrical tingling under power lines

It's been happening to me for years. I finally decided to ask users who are better with "practical physics" when I was told that my experience – that I am going to describe momentarily – prove that I ...
22
votes
3answers
5k 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 ...
21
votes
6answers
3k views

Could someone intuitively explain to me Ohm's law?

Could someone intuitively explain to me Ohm's law? I understand what voltage is and how it is the electric potential energy and that it is the integral of the electric field strength etc. I also ...
20
votes
5answers
3k views

Does alternating current (AC) require a complete circuit?

This popular question about "whether an AC circuit with one end grounded to Earth and the other end grounded to Mars would work (ignoring resistance/inductance of the wire)" was recently asked on the ...
19
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2answers
3k 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 ...
17
votes
4answers
2k views

Are voltages discrete when we zoom in enough?

Voltages are often thought of as continuous physical quantities. I was wondering whether by zooming in a lot, they are discrete. I feel like the answer to the above question is yes as voltages in the ...
16
votes
4answers
4k views

What's the physical meaning of the imaginary component of impedance?

As you know, impedance is defined as a complex number. Ideal capacitors: $$ \frac {1} {j \omega C} \hspace{0.5 pc} \mathrm{or} \hspace{0.5 pc} \frac {1} {sC} $$ Ideal inductors: $$ j \omega L ...
16
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3answers
1k views

Distorted colors of Google StreetView photographs near electric power lines

This is a followup to my question: Cyclist's electrical tingling under power lines Some users presented a convincing picture that the electric shocks under power lines are primarily from the ...
13
votes
5answers
6k views

How can Ohm's law be correct if superconductors have 0 resistivity?

Ohm's law states that the relationship between current ( I ) voltage ( V ) and resistance ( R ) is $$I = \frac{V}{R}$$ However superconductors cause the resistance of a material to go to zero, and ...
13
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11answers
14k 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 ...
12
votes
5answers
2k views

Is current in superconductors infinite? If they have 0 resistance then I (V/R) should be infinite? [duplicate]

I learned many years ago that according to Ohm's law, current is equal to voltage divided by resistance. Now if superconductors have zero resistance then the current should be infinite. Moreover the ...
12
votes
8answers
27k 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 ...
12
votes
5answers
927 views

Why are wires in simple circuits approximated as equipotentials?

I just answered this question: Voltage in a circuit by asserting that any two points joined only by a wire, but no other circuit elements, are at the same value of the electric potential. It is, of ...
12
votes
2answers
294 views

Is there a simple proof that Kirchhoff's circuit laws always provide an exactly complete set of equations?

Suppose I have a complicated electric circuit which is composed exclusively of resistors and voltage and current sources, wired up together in a complicated way. The standard way to solve the circuit ...
10
votes
2answers
3k views

Where does electricity go from a solar panel that is not plugged in to anything?

I found a similar question here on this site, but my question is slightly different. If a solar panel is exposed to sunlight but is not plugged in to anything--dc load, inverter, etc--where does that ...
10
votes
3answers
750 views

How does electricity 'decide' on it's pathway? [duplicate]

I'm struggling to understand the fundamental concepts of electricity, more specifically, the way in which it 'chooses' its optimal pathway. I appreciate electricity will always choose the path of ...
10
votes
3answers
575 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 ...
9
votes
4answers
6k views

Resistor circuit that isn't parallel or series

What's the equivalent resistance in this circuit (between points A and B)?
9
votes
2answers
2k views

How does my hand amplify an FM radio signal?

I have a gizmo that broadcasts an FM radio signal from my phone's headphone socket to my car's radio antenna. Sometimes, there's another station on the same frequency with a stronger signal and my ...
9
votes
3answers
66k 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.
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 ...
8
votes
2answers
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 ...
7
votes
5answers
799 views

What causes contact resistance?

When two components are combined in an electric circuit, there is apart from their own resistances a contact resistance at their junction. This causes a sudden voltage drop of ...
7
votes
6answers
11k 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 ...
7
votes
3answers
6k 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.
7
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3answers
12k 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 ...
7
votes
4answers
2k views

Symmetry in resistor circuits

Given 6 points that are connected with each other with a resistor of resistance $R$, find the resistance between any two points. (Answer: $R/3$) (All the conducting wires have the same ...
7
votes
3answers
5k views

Path of an electron through an electric circuit

When a potential difference is applied across a conductor, and if an electron moves from the negative terminal of the battery and reaches the positive terminal, then I want to know if the electron ...
7
votes
1answer
773 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 ...
7
votes
1answer
382 views

Reluctance of torus shaped iron core with embedded wire loop

Imagine a circular wire loop (r = 50mm), the wire has an assumed diameter of zero, which is embedded in a torus shaped iron core with a circular cross-section of R = 10mm. A current in that loop ...
6
votes
3answers
4k views

What happens if I throw a battery into water?

Today I have by accident thrown a AAA battery into a bucket of water. I fished it out of the water immediately (within 20 seconds or so) and nothing notable had happened and the battery is still full ...
6
votes
3answers
4k views

Can single DC 1.5V battery generates 1500 Watts power?

Suppose there is a DC $1.5\mathrm{V}$ battery connected with $1.5\times10^{-3}\mathrm{\Omega}$ resistor. Then the amount of circuit current is $I=V/R=10^3\mathrm{A}$. (according to Ohm's law) I know ...
6
votes
6answers
28k views

In an alternating current, do electrons flow from the source to the device?

If electrons in an alternating current periodically reverse their direction, do they really flow? Won't they always come back to the same position?
6
votes
7answers
11k views

Does a current carrying wire produce electric field outside?

In the modern texts of electromagnetism in the presence of stationary currents the electric field is assumed conservative $\nabla \times E =0 $. Using this we get $E_{||}^{out}=E_{||}^{in}$ which ...
6
votes
4answers
2k views

What is the current of a capacitor when the derivative of voltage is undefined?

This is from the textbook I am reading: I know this equation for capacitors: $$i=C\cdot \frac { dv }{ dt }$$ Here is my question: how can diagram (a) be allowed if the derivative of the voltage ...
6
votes
4answers
2k views

Why do electric motors draw current even when they are not moving?

After testing electric motors, I realized that these motors draw current even when they are not moving. I do feel that these motors are trying to move, but they are not really moving, in the end. ...
6
votes
1answer
1k 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 ...
6
votes
1answer
1k views

How can I put a permanent current into a superconducting loop?

I know that you can use induction to create a current in a superconducting loop, but this only works as long as the coil that induces the field has a current flowing through it. And obviously, this ...
6
votes
2answers
195 views

$V=IR$, isn't it missing something?

So I know that $V=IR$ works for circuits, but for the case of an arc-before the arc jumps, there is a potential difference, but no current, but there isn't infinite resistance is there? I don't ...
6
votes
2answers
3k views

How electric currents can flow between 2 points at the same potential?

According to Ohm's law, if there is a potential difference, $V$, across a resistor then there is a current, $I$, flowing through it. Since we assume that points along the connecting wire are at the ...
6
votes
2answers
824 views

Will I get a shock when I try to use my hair-dryer under water?

Occasionally people get killed in their bathtubs by having an electrical device such as a hair-dryer take the bath with them - in movies. It seems to be a common belief that this is realistic, even ...
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 ...
6
votes
6answers
5k views

What is Electromotive force (EMF)? How is it related to potential difference?

What is Electromotive force (EMF)? How is it related to potential difference? Is it the creation of potential difference in any conductor??Is it a process?Why is it called force? Does writing emf ...
6
votes
0answers
63 views

Weird phenomenon on aluminum laptop casing [duplicate]

A couple of days ago I observed a phenomenon which I'm not sure I understand correctly. My brother-in-law has recently bought an ASUS gaming laptop in an aluminum casing. When the power supply is ...
6
votes
3answers
993 views

Why can't a superconductor make a DC motor self sustaining?

Superconducting wire can host a low current magnetic field. I do not know if it supports a corresponding electrical field. Can a superconducting wire that sustains a current accelerate a DC motor? ...
5
votes
5answers
1k views

How does insulating footwear prevent an electric shock?

The reason I have always heard to explain the reduction of electric shock when we wear insulating footwear goes as follows: When electricity passes from our body to the ground, an electric circuit ...
5
votes
4answers
12k views

How does power consumption vary with the processor frequency in a typical computer?

I am looking for an estimate on the relationship between the rate of increase of power usage as the frequency of the processor is increased. Any references to findings on this would be helpful.
5
votes
1answer
3k views

How can KVL & KCL be derived from Maxwell equations?

How can KVL (Kirchhoff's Voltage Law) & KCL (Kirchhoff's Current law) be derived from Maxwell equations in lumped circuits?(Lumped network : if $d$is the largest dimension of the network and ...
5
votes
3answers
570 views

How is Kirchhoff's voltage law understood in the water flow analogy?

I met the Kirchhoff circuit laws in the past, but now I'm trying to associate them with a practical representation to be sure to understand them. Let's start with the Kirchhoff current law: If I say ...