# Tagged Questions

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

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### Does charge of capacitor at constant voltage change after dielectric material is inserted?

I have a planar geometry capacitor, connected to a battery that supplies V volts. Initially there is vacuum/air in between both plates. Afterwards, some dielectric material is inserted in between both ...
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### Switching on a light bulb. Initial EM/electron pulse propagation

TLDR When switching on any electrical device (e.g. a light bulb or a heater), there is an initial wave (pulse) travelling with very high speed (close to light speed) and “carrying the information” ...
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### Nature Of Bulb Glowing In Parallel LR circuit with bulbs

In the given circuit the switch is initially closed and then opened after some considerable time.Then which bulb will stop glowing first? Which bulb will glow more brightly?Why ? .After opening ...
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### Can electricity flow through vacuum?

People say yes, and give a wonderful example of vacuum tubes, CRTs. But can we really say that vacuum (..as in space) is a good conductor of electricity in a very basic sense?
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### Is there any example where electric and magnetic fields are not perpendicular?

Perpendicular electric and magnetic field creates light or other electromagnetic waves. Is it a necessary property to have a perpendicular fields? If not what would happen when the fields are not ...
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### When potential difference is equal to the emf, isn't the current 0?

I have been told that the $emf$ is equal to the potential difference across the terminals of a cell when no current is flowing. Does that mean that the current is zero ($I=0$)?
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### How feasible is it to power your home with a bicycle? [on hold]

This article claims "60 Minutes On This Bicycle Can Power Your Home For 24 Hours!" How feasible is this claim? Sounds great - but the skeptic in me says "yeah, right." Hope this is an acceptable ...
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### Why is there no current flow when i connect two opposite terminals of two separate batteries

I don't understand this..maybe there is something wrong with my understanding of battery or electricity. I am learning about electricity more deeply this time. So please spare with me... So lets ...
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### 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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### Charge of electron in AC/DC circuit

If electrons in a DC circuit going through a metal wire carry only negative charge from negative to positive, then in a AC circuit through a wire does a electron carry both a negative charge and ...
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### Bulbs glow with different brightness in one arrangement and the same brightness in the other arrangement

The question is: Mr.X decorated his house with fairy lights on a celebration.He bought 40 bulbs and operated at 220V. He found all the bulbs are glowing with different brightness. He called his friend ...
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### What does an increased time constant of a capacitor do?

If a capacitor is being charged to any voltage, what effect would increasing the time constant have on it and if a graph of Charge Q/Time T was plotted to give a positive decreasing gradient, how ...
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### Possiblity for particle to be carried by a wave such as a photon or electromagnetic wave/waves in general for means of transportation/travel? [closed]

I am wondering whether it is possible for a photon/EM wave to carry a very small particle like an elementary particle or smaller on it like a highway carries a car traveling on the highway or an ocean ...
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### Physical interpretation related to a non-linear partial differential equation

I am doctoral student in pure mathematics working on a particular problem. My question is if this problem has applications to real world phenomena. I will try to explain the direct problem starting ...
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### What happens to metal when exposed to an electric current for an extended period of time?

I was wondering what happens to the actual metal (copper, aluminum, silver, gold) when electricity is ran through it for a long period of time. Say years like the wire in a house. Does the ...
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### Comparison between current and voltage sensitivity

Current sensitivity of a galvanometer is defined as deflection per unit current, $$\frac{\phi}{I}=\frac{NAB}{k}$$ Here, $\phi$ is the angular deflection, k is the torsional constant of the spring, ...
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### Microscopic fields inside a conductor

In a neutral conductor if we assume electrons as point charges, the electric field in the space between them cannot be identically zero. This microscopic field may be very weak. What if we were very ...
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### 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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### Why does a cathode have to be heated to emit electrons?

Considering that electrons are highly mobile inside of a metal, why do they have such a tough time getting out at the edge of it and continuing their trip ballistically?
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### Magnet dimensions for 3-phase permanent generator

I'm making a 3-phase permenant generator. According to Faraday's law, the emf produced is negative number of turns times the change in magnetic flux over the change in time. If it is only the CHANGE ...
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### Question regarding Van De Graff generator Belt

I have made a VDG generator with a rubber band as the belt and a glass roller. It doesnt seem to work because I think the rubber band may be conductive. I was thinking of using other materials for ...
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### Current carrying conductor

In a current carrying conductor, the net flow of charge is zero. Is this possible? Arent the charges moving? Are the charges moving in a current carrying conductor?
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### Charging Copper ball bearing

I want to conduct an experiment to observe the trajectory of charged particles in applied magnetic and electric field. Thus, I want to charge a copper bead/ball bearing. How can I electrically charge ...
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### Why don't get I shocked in an electric shower if the resistance makes contact with water?

I've found this image that perfectly illustrates my shower. I've read somewhere that the resistance is insulated so even if it touches the water, it doesn't conduct. However, as you can see, the ...
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### Potential Difference

Ohm's law: $$V=IR$$ Here $I$ is the current in the circuit, which is equal to charge flowing per unit time. $R$ is the resistance offered. $V$ is potential difference. What's the physical ...
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### Trouble understanding Electric flux and gauss law

Well, i know that the electric flux is the number of field lines passing a certain area, but (1)what does that mean? I can't the concept itself. I know it have many applications, gauss law one of them,...
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### Which of the following has higher resistance - milliammeter or ammeter?

The question is the same as the heading - Which of the following has higher resistance - milliammeter or ammeter ? Now my teacher's and my answers don't match. It is assumed that the spring constant /...
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### Direction of AC current in a very long wire [closed]

Suppose an external wire of length 10^8 meter (very long indeed) is connected in between the slip rings of an AC generator externally. Taking the speed of current propagation to be ~10^7 m/s, then it ...
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### Electron Beam does not appear to be continous (CRT Experiment)

https://www.youtube.com/watch?v=2xKZRpAsWL8 Why do you see patches of purple in the tube? Shouldn't there be continous lines of colour? As far as I know, you see the rays because some of the ...
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### Why does static charge build up and how do I prevent it?

I bought my 11-month-old son a tricycle from Smart Trike (official website) and I have noticed that after a few laps indoors on my marble floors static charge would build up in him as I can see his ...
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### Is a straight lightning bolt possible?

Recently, I saw a demonstration where an annealed steel rod and a hardened steel rod were made to fail from tensile stress (they were pulled on like an elastic band and snapped in a vice-like machine) ...
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### What is the average range of voltage of lightning in sky?

I wondered how much energy is required to produce , such a loud sound? What is the average range of voltage in sky? Is there any possible way to store it ,and use when needed?
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### What is the maximum amount of electricity I can draw in 48 hours from a domestic supply? [closed]

An electricity company is offering free electricity for a 48 hour period every week. The rate the rest of the time is very expensive. How much power can be drawn from a domestic UK supply? Would it ...
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### Electrical equivalent of inverted pendulum

Background I am working on a summer project to design labs for undergraduate students. One of the topics is feedback and there is already quite a lot of stuff about passive feedback, so we might add ...
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### Energy dissipation in current flow

In section 4.8, Energy dissipation in current flow, of Purcell and Morin's Electricity in Magnetism, the expression for the power expended by a resistor is derived. The sections includes the following ...
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### What can justify the decrease of the electrical conductivity with the increase of light intensity?

I have currently been working with a sample that "appears to" decrease its resistance when I cover it and protect it from light. Basically it presents the opposite behaviour of a photoresistor. What ...
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### Is there an electric field around neutral atoms?

Even if the atom is neutral (equal numbers of protons and electrons), the electrons and nucleus form an electrical dipole, so there is still an electric field around them, even though the total charge ...
39k views

### Why does voltage remains same over Parallel Circuit

Why does voltage remains same over parallel circuit. If a resistor is connected in the circuit some of the charge should be transformed into heat and make a lack of charge after the resistor (in my ...
634 views

### Do electrons lose energy between the battery anode and cathode?

In a battery circuit, does an electron leaving the anode carry more energy with it than an electron returning, from having been through a machine, to the cathode? If not, how does the battery deliver ...
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### Basic concepts of electrostatics

How to deal with a grounded conducting sphere (I.e finding charge on it) in uniform electric field ? And if any two charged conducting spheres are in each other's electric field then will ones field ...
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### Can Light Really be Matter? [closed]

I remember during my early education being taught that light is a form of matter. This has always seemed counter-intuitive to me.
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### How pseudocapacitors work?

I have read that pseudocapacitors are combined of a carbon electrode and a metal oxide one. On the carbon electrode simply a double layer is built up and on the other some chemical actions(redox) ...
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### Why Electric current is considered fundamental quantity [duplicate]

It seems to me electric charge is more fundamental than electric current. Can anybody explain why electric current is taken as fundamental quantity and not electric charge?
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### Force on a magnetic dipole due to a magnetic field

Imagine a solenoid which has current $i$ and is producing a magnetic field $B$ which equals $$B=\mu N i$$ Now, imagine we put a small cylindrical magnet at the end of the solenoid. Then because at ...
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### How did physicists know that only negative charges move?

I have phrased similarly another question about how physicists knew that two charges exist, positive and negative. The purpose of the question is not necessarily to educate me historically. It's just ...
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### Is it possible to transform chemical energy in electrical energy by modifying the equilibrium constant?

Considering a Daniell cell, is it possible to create endlessly electrical energy by using atmospheric temperature (for example) variations to modify the reaction's equilibrium constant ? I apologize ...
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### Static electricity and insulators

I've read that Stephen Gray in his experiments on electricity, he has found that static electricity can be conducted -transferred- through an insulator thread made of silk. So, how could that happen ...