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

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power in an ac circuit - difference between in series and parallel

In AC-circuits, we have different kinds of power: active power $P$, reactive power $Q$ and apparent power $|S|$. Let's say we have a circuit with a resistor $R$ and an inductor $L$. My understanding ...
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2answers
73 views

How could a solar eclipse cause my light bulb to explode? [closed]

Any explanation to this? as it happened right during the phase of eclipse or is it just coincident? I had just finished my breakfast and on the way to go outside to watch the eclipse and before it ...
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1answer
17 views

Does electron drift model apply to current in liquids

The electrons in a metallic conductor, tend to drift at abysmally slow speeds, but still a current is able to flow through it, because the net movement is in the direction of the applied emf. How is ...
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32 views

How does the jumper in Christmas lights work?

This is the structure according to my textbook: I don't know what the glass insulator are for?? But there is indeed a thin layer of insulator coating on the jumper. Why I don't know, too, what that ...
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143 views

Electric Honeycomb

Set a vertically oriented steel needle over a horizontal metallic plate. Place some oil onto the plate. If you apply constant high voltage between the needle and the plate, a cell structure appears on ...
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9 views

Discharge Static Electricity from Carpet without chemicals

I've got a large amount of static electricity built up in a room. Is there any way I could discharge the static without the use of chemicals?
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69 views

How can the fact that there is no electric field inside a hollow conductor be explained by Faraday's ice pail experiment?

Basically something very similar to these pictures These are from two separate books. The bottom picture says that all the excess charge in an object can be transferred to an already charged metal ...
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1answer
215 views

Why don't we feel shock when there is lightning? [closed]

When there is lightning in the sky and I am are standing on the ground having no insulating material between me and the ground, why do I not feel an electric shock? If this looks stupid to you I am ...
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1answer
32 views

What are the clicking sounds when static electricity occurs?

Sometimes, when there's static electricity, soft clicking sounds can be heard. This may happen when two fabrics are rubbed or when you get a static shock. What exactly causes this sounds?
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26 views

Proving an AC current with peak amplitude of 311V is equivalent to a DC current of 220V [closed]

If one starts with an alternating current in the form of a sin wave with a peak amplitude of 311V and then goes through the usual RMS procedure of integrating $sin^2$ from 0 to 2$\pi$ then the result ...
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57 views

What phenomena occur in a low voltage arc between copper and graphite electrodes, and why is the result dependent on electrode polarity?

I was playing around with a laboratory power supply, drawing arcs between electrodes of various materials. I noticed phenomena that I found interesting, and couldn't really explain myself: The ...
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25 views

The Photoelectric Effect in passive cooling?

Information on the Photoelectric Effect: https://en.wikipedia.org/wiki/Photoelectric_effect Summary: Some metals release electrons when struck by a certain frequency of photon. What does this mean ...
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33 views

How is it possible to even develop any current in an inductor?

Potential difference across an inductor (ie p.d. between current exit point and current entry point) is given as $$V= -L\frac{di}{dt} -iR,$$ where $L$ is the inductance of inductor and $R$ is its ...
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53 views

What does the movement of charge in an object mean?

When it is said that charge "moves" throughout an object, like if negative charge moves to the edge of an object and the charges become polarized, does this mean that the electrons has moved to the ...
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1answer
38 views

Will putting a rubber cap on a steel bar prevent it from getting struck by lightning?

Let's say there's a stainless steel bar pointing to the sky from the ground. Like this there's a possibility it gets struck by lightning. Now would putting a rubber cap on top of the bar change this ...
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1answer
43 views

Error in current voltage relation? [closed]

The current voltage relation of diode is given by I=(e^(1000V/t)-1)mA,where the applied voltage V is in volts and the temprature T is in degree Kelvin. If I made an error measuring +-0.01 V while ...
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66 views

How quick does a regular household bulb lights up after being switched on? [closed]

In this video the narrator mentions a study in which if a light bulb lights up quicker than 40ms it would seem as though it lit up before it was even switched on. How quick does a regular household ...
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3answers
40 views

Why is it that when potential difference across a capacitor is equal to the supply voltage, no flow occurs?

Can someone explain to me how and why this happens? I'm really confused. I'm also confused about how the net charge between 2 plates is 0.
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31 views

What happens when we connect one end of a wire to the main supply and the other end to ground?

If we connect a wire to the main supply(240v) and if we ground it, what will happen ?? Will there be a current flow ? Will I get a huge electricity bill at the end of the month ?? Also if we connect a ...
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24 views

Negative ampere and graphical convention

Since only electron's flow in electricity and electrons have negative charge, then why we don't say —1amps (—1C/s)? Secondly, as conventional way we write down independent variable in $x$ axis and ...
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32 views

Can an Oven being set to a different temperature cause electric board to go off?

Basically: the electrical system kept going off (when light goes down in a division due to too many electrical appliances on at a time, or their combined power consumption). My roommate said it was ...
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1answer
29 views

tranfser of electrons between two metals and a wire

If you have a circuit of a battery, a Resistance and a light connected with a wire by example: in the middle the wire is cutted in two pieces. if you connect each piece of wire with a metal object and ...
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110 views

How much is a Coulomb, really?

I've heard it said in my physics class that a Coulomb "is a lot of charge". And I believe it; most of the problems I've done in the class so far involve charges on the order of micro-Coulombs (or, ...
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52 views

Drift velocity of electrons in a conductor

How does the drift velocity of electrons in a conductor depend on the temperature? I have two contradicting views for this. First, we can say that increasing the temperature of the conductor will ...
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1answer
64 views

Why do we prefer using materials of high resistivity in laboratory instruments?

I know that :$$R=\rho\frac{l}{A}$$ where $R$ is the resistance of the wire, $\rho$ is its specific resistance (resistivity), $l$ is its length, and $A$ is the area of cross-section of the wire. Why ...
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Doesn't any massive conductor look like “ground” to an AC supply?

I've been puzzling over this excellent answer to the perennial "Why don't I get shocked by a hot wire if I'm not grounded?" question. The orders of magnitude just don't seem right for two reasons: ...
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24 views

How to insulate static electricity

This is a follow up question to Extending the reach of a crocodile clip for Kelvin Water Dropper experiment. We have resolved the issue, but now we have the following cable (in the image) that ...
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3answers
87 views

How can the copper wire in an electricity generator provide an infinite number of electrons? [closed]

How can copper wire in an electricity generator produce an infinite number of electrons when the is a finite number orbiting each copper nucleus?
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49 views

What effect does voltage have on electron energy levels? [closed]

Is there any effect at all on an electron's energy level when subjected to a voltage?
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71 views

Are there alternatives to steam in thermal power stations?

'A thermal power station is a power plant in which heat energy is converted to electric power. In most of the world the prime mover is steam driven. Water is heated, turns into steam and spins a steam ...
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1answer
33 views

Direction of AC current in a very long wire [closed]

Suppose a wire of length 10^8 meter is connected in the slip rings of an AC generator. Taking the speed of current propagation to be ~10^7 m/s, then it takes 10 seconds for current to flow from one ...
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46 views

How paper strips get electrified?

Why paper strips get electrified when we iron them? I have learned that when two insulators are rubbed then they gets electrified but in case of ironing a paper the iron is a conductor. Will rubbing a ...
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1answer
107 views

Why does a battery die more quickly when more resistors are added to the circuit?

I will be explaining what I think: A battery acts like a pump which provides energy to do work on negative charges to move them towards the negative terminal, and hence creating an electric field. ...
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30 views

Why is lightning going from the Earth to the clouds while the electrons are going from the clouds to the Earth?

The lightning is often a discharge in advance. The (negative) charge slide occasionally a little further on in the conductive channel, wherein said channel is highlighted each time something. The ...
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91 views

Why does a higher wattage incandescent light bulb have a lower resistance value than a lower wattage incandescent light bulb

I am an electrician and know through experience that resistance in an electrical circuit causes heat. An incandescent light bulb's light is a by-product of heat, so why does a 100w bulb have a lower ...
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24 views

Measuring Static Electricity

Is it possible to measure the static electricity in a room using a VOM or some other digital meter? I have a lot of static electricity building up in a carpeted room, and would rather not spend the ...
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83 views

What makes Jacob's ladder spark to go upwards?

In a Jacob's ladder (https://www.youtube.com/watch?v=GaC4BnbH1NY&index=3&list=PL_SAbPKia2YMFi-t8z5WFYCd86Plcs1Un) a spark is originated in the bottom and climbs up to the top. I have read in ...
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41 views

what would happen to flowing electrons in a vacuum if they are not giving any exit point?

Lets say theoretically electron flow is captured in a vacuum and not allowed to exit then where would they go? I do not want to know the practical impossibilities of it. And also what would happen if ...
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64 views

Touching one end of a battery

What happens when I touch one end of a battery? Is there any flow of charge from the battery to my body? I know that connecting a battery to both ends of capacitor causes the charge from one plate ...
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1answer
53 views

What is the dielectric constant of a pure conductor?

Dielectric constant is the ratio of permittivity of a medium to the permittivity of free space. How to find dielectric constant of a conductor?
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45 views

Explanation of duration of forces due to electrostatic charge

when we use the pen and make the rubbing in it the pen can attractive the paper and after 1 sec. the paper fall down because it loss the earned energy but in this video the balloon still attractive ...
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1answer
75 views

Why does compton scattering provide evidence for the particle nature of light?

I understand that compton scattering is modeled as a collision between a photon and an electron, but why does this conclusively prove that light can act as a particle? Why couldn't the same ...
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1answer
96 views

How is a variable potential divider able to reduce current/voltage through a component to zero, unlike a variable resistor?

For example, the diagram in my text book shows a filament lamp, in series with a uniform resistive wire, which can have its voltage and current varied by moving the sliding contact, e.g., a ...
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2answers
48 views

When heat loss is more than energy generated [closed]

Suppose a electric power station produces 200W of electricity @ 200V. Now instead of stepping it up, it decides to transmit it as 200V to a city 20 km away. The transmission cable has resistance per ...
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43 views

Why does a variable potential divider have the ability to reduce current through a component to zero

For example, the diagram in my text book: shows a filament lamp, in series with a uniform resistive wire, which can have its voltage and current varied by moving the sliding contact, e.g., a ...
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3answers
55 views

Radiation due to current

Generally we equate change in potential energy to change in kinetic energy but in case of a charged particle like electron this is inconsistent. Consider a case: An electron(of charge e)from rest is ...
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23 views

Separating Interaction of Heat from Electricity?

I have a rod where electricity of frequencies 1-360 Hz is passed through. It is affected by heat. I am evaluating the energy involved in such a process, contributed by electricity and heat. The ...
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14 views

Effect of Electric charge on balloon [closed]

I recently provided a charge to a (inflated) balloon which popped within seconds of introducing the charge ? Why so?
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28 views

Is the $I^2R$ when a resistive heating element is cool the same as when it's hot?

My system (electric resistance element and water bath) heats up 2 degrees in 20 seconds (0.1 deg/sec) when the resistance element if fully heated. Say I want to raise the temperature 0.1 deg every ...
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39 views

Extending the reach of a crocodile clip for Kelvin Water Dropper experiment

We're doing a physics project that involves a version of the Kelvin Water dropper experiment. Everything is working great, and we have the following system: In the image: two plastic containers ...