The study of the presence and flow of electric charge. Charges, currents, fields, potentials.

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Electrons flowing through a circuit make it warm, where does that heat come from

in a circuit I have a low resistance device that consumes many watts, in normal operation this device will get warm; where does this heat come from? the law of conservation of energy states that the ...
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1answer
48 views

Why not run a cable from the north pole to the south pole to access its energy (magnetic or electrical)

Would a cable tied to the North Pole around the curve of earth downwards to the South Pole give us access to a HUGE AMOUNT of energy (magnetic or electrical) by linking into it.
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2answers
36 views

How is electric field instantaneously generated inside a conductor connected across two terminals of a battery? [duplicate]

I have learnt that the electric field that is responsible for current flow is generated inside a conductor as soon as the two ends of the conductor are connected or brought in contact with the two ...
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1answer
37 views

How soon would electrons start flowing once I closed a switch on a circuit that was one light minute away from the battery

In a circuit, how do electrons "know" when the circuit is closed? To my understanding, they do not start flowing unless the circuit is closed. How soon would they start flowing once I closed a ...
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1answer
36 views

Why does not the electrons in a conducting the wire end?

What happens to the electrons in a conducting wire, Why does not the electrons in the wire end? I have read answers on the web but have not manage to understand, the free electrons from the ...
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2answers
47 views

How are superconducting magnets powered?

Since the resistance of a superconducting circuit is exactly 0, it would try to draw infinite current from a power source, since P=I^2*R. For a finite power source, I-> infinity as R->0. Correct? ...
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1answer
19 views

The speed of an electrical signal through different mediums [closed]

This is sort of a bio physics question and it comes in two parts. The first is: what is the speed of an electrical signal through human nervous tissue? The second part is: what is the speed of an ...
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1answer
89 views

How to solve difficult resistance puzzles? [closed]

How does one solve really difficult resistance puzzles? These are presented in the form of a diagram with multiple resistances in various combinations. I have done some puzzles by reducing the puzzle ...
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1answer
94 views

When you smooth-en a surface at microscopic level, friction increases. Why?

When I was learning a chapter related to Static electricity, my teacher had mentioned that when you rub your comb with DRY hair specifically, static electricity is generated due to friction. Further ...
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2answers
68 views

The source and sink phenomenological description of charge - how realistic is it?

I've heard over and over an electron described as a source of the electric field, but that is a misleading term. Source makes one thing of a tap, with a constant flow of something coming out of it. ...
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44 views

Energy in conductors with $\vec{E}$-field

The question is deceptively simple. Suppose I have a uniform circular wire in which I have created the a E-field by some mean. We that without the source the electric field should not be there, so if ...
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2answers
53 views

Would an ordinary or fluorescent lightbulb generate electricity when exposed to light?

I was wondering whether the physic laws or the nature in which lightbulbs are constructed would allow for lightbulb to generate electricity when subjected to strong (intensive and concentrated) ...
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79 views

Relation between power & thickness of the filament

Tell me what relationship is used to solve the question given below. There are three bulbs of power 60, 100 and 20; which one has thickest filament for same source? (a) 100 (b) 20 (c) 60 ...
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2answers
118 views

An infinite value for an electric field?

Consider a system of point charges. To calculate the value of an electric field at a point, we consider the contribution of the electric field from all the charges at that point. Consider the ...
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2answers
78 views

Potential difference inside charge distributions

Always when I think about potential difference inside a symmetrical charge distribution, I think of it being equal to zero because it's dependent on the field and I imagine the directions of each of ...
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1answer
85 views

Difficulty understanding electricity concepts

In circuit diagrams what does it mean for energy to be used in going through a component? I usually see this when emf is being described: total energy supplied per coulomb by battery = total energy ...
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2answers
285 views

How can we know that a particular charge is positive or negative?

Suppose I am provided with a positive is charged....and someone tells me to find which type of charge is present in it? Then how can we detect that the body is positively or negatively charged? Is ...
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2answers
43 views

Simple Circuits [closed]

I have a small and easy dilemma, judging by how sophisticated the website is, and need a simple answer for it So $P=E/t$. And $P=I*V$. Therefore $E/t=I*V$. I just need an explanation on how this is ...
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140 views

Is there no electric field inside a conductor?

I came across this statement while studying electric currents and I am confused: "There is no electric field inside a conductor. Hence no current can flow through it". Is there a fallacy in this ...
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2answers
79 views

Calculating average energy stored in Li-Po battery

I'm currently sourcing Li-Po batteries and need to find an average mAh per cm3 to implement it into my product. From what I read (wikipedia), the energy density of Li-Po ranges from 250 to 730 W.h/L ...
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1answer
120 views

The Electric Quadrupole

I've read the following sentence: "Every electric circuit with two pairs of accessible terminals is called a quadrupole." I was wondering why does it happen that the multipole expansion gives us a ...
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1answer
53 views

Wireless energy flow through earths magnetic field

Seeing that technologies such as that developed by WItricity are based on magnetic fields, is it possible to transfer electricity that way through earths magnetic field?
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1answer
147 views

Understanding the relationship between electric energy and force

I'm trying to do the following problem: One of the three types of radioactive decay is "β decay", during which protons decay into neutrons or vice­versa, emitting either electrons (β­) or positrons ...
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1answer
321 views

Static Electricity - Plastic comb, hair and small pieces of paper doesn't work for me? [closed]

All I have to do is run the plastic comb through my hair and hover it over small pieces of paper, right? The comb should then be charged and attract the pieces of paper... but that doesn't seem to ...
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2answers
97 views

What can happen when 2.3*10^28 positrons collide with 2.3*10^28 electrons? [closed]

I'm interested in this question after a writer friend asked me what happens when a human gets bombarded with positrons. Didn't want to post this under scifi because I want more "scientific" answers... ...
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1answer
16 views

AC Resonances - Reduction In power

I am having trouble understanding the following; Because the Q value is based on the bandwidth at the 3dB points in the frequency transfer function, we need to find a way to measure these. In our ...
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3answers
293 views

Electricity consumption in fan

Does regulation in a fan vary in Electricity consumption? i.e. I want to know exactly, is the energy consumption more when regulator is tuned to highest number or lowest number?
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2answers
576 views

Why is static electricity called static?

They called it "static" because "it doesn’t go anywhere". In order to create static electricity, you have to rub two different materials. When you rub them, the electrons move. So, why is it called ...
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2answers
146 views

Whats the point in conserving electricity if the AC current produced cannot be stored?

If we cannot save the ac current produced in a battery or some device like the DC current there is no point in conserving it because current once produced should be consumed somehow!!
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1answer
162 views

The Electric field & Coulomb's law [closed]

A point charge is moving in an electric field at right angles to the lines of forces .Does any force act on it ? Please explain why.
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3answers
938 views

Polarization vector of dielectric electrostatics

I know two laws for Polarization vector of a dielectric material $$\vec P = N q \vec{\Delta L}$$ Where $N$ is the number of dipoles per meter cube, $\vec{\Delta L}$ is the vector that represents the ...
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1answer
2k views

Electric Field of a circular arc at a point

Given that the circular arc wire with radius 'r' has a linear charge density λ. What is the Electric field at the origin? I took a small segment dy, which is 'θ' above the x-axis with charge ...
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2answers
2k views

Why the current decreases with increase in voltage in transmission lines? But according to Ohm's law current should increase with Voltage

Is the Ohm's law violated here? And also why is electricity generated at 11,000 V in India?
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2answers
586 views

What's the relation between output voltage and time to boil water given the same kettle?

An electric kettle rated 220V, 2000W needed 10 minutes to boil water when it is half filled with water in Singapore where the output voltage is 220V. Estimate the amount of time needed to do the ...
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1answer
72 views

Does this person get electrified?

Does a person get electrified when his feet are on the floor, his right hand is holding $220~V$ and his left hand holding a piece of wood or any other insulator?
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59 views

Can I calculate the current of any setup with capacitance by the same formulae?

There are known formulae relating a capacitor's voltage and current in its classic form (battery, wires, a capacitor circuit), but what if we had a charged plate (-ve), then we put on one of its ...
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1answer
51 views

Electricity supplication [closed]

Is their any reason I can search up as to why electricity is generally harder to inaugurate in regions of vast inhabitability?
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1answer
347 views
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523 views

Heat loss using alternating current

I am looking for somebody who can explain this to me. As I have read in physics books, the Joule-Lenz Law (Joule effect of heating) is represented by the formula: $$ W = I^2Rt $$ which can be ...
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1answer
41 views

Form factor and average value [closed]

Why Our Electricity Flowing in the Sequence of 11kv,33,66,132kv,why not Flow in 10 kv,11,12,13,14 that Sequence.
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2answers
55 views

How is the wattage of electrical appliance specified?

What does it mean by a bulb is 60 Watt or 100 watt (I know it means it emits 60 or 100 Joules of energy per second, but at what conditions)? Which one glows brighter when connected in series?? What ...
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2answers
1k views

Water and electricity? Hot or Cold?

Is hot water or cold water more conductive for electricity or is it the same regardless?
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3answers
354 views

Creating electricity from mains water pressure.

Could someone cleverer than me help me out? I had a crazy thought going through my head the other day and I can't lay my mind to rest until I get an answer. Q. How much energy could be produced by ...
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2answers
822 views

Photoelectric effect: current vs wavelength

In an experiment where the type of metal,intensity of light and potential difference across a battery is kept constant at 2V the results show that an increase in wavelength, obviously in turn ...
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2answers
53 views

How much electricity can be generated from ambient sources?

I know that recent advances in technology are doing amazing things with very low amounts of electricity, with RFID being one of the most familiar examples, but I'm not very familiar with the ...
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1answer
835 views

The effect of high frequency AC current in a fresh corpse [closed]

Given two AC currents of the same intensity, eg 20 mA, but different frequency, 60 Hz and 20MHz, which one would be more likely to reach the heart ? I've read about the skin effect and how current ...
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1answer
249 views

Superposition theorem

Is superposition theorem applicable for circuits having semiconductor components like diodes, transistors, etc.?
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1answer
1k views

What is the maximum theoretical efficiency of heat to electricity conversion?

I know that heat engines (heat to kinetic) are limited by Carnot cycle and that kinetic energy to electric energy conversion via standard generator reaches over 90%. However I would like to know ...
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3answers
634 views

electron flow in capacitor with dielectric

if I make a circuit with a battery and a capacitor (with a dielectric inside), how it is possible to get a current in the circuit? If electrons go from one pole of the battery and they arrive to one ...
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2answers
483 views

What actually happens at the microscopic level in a Zener diode in reverse bias?

A Zener diode is used as a voltage stabilizer. The graph of current vs voltage of Zener diode clearly shows that there is a constant voltage across Zener after the breakdown voltage as the current ...