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

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Voltage and Current

I know that as voltage increases, current increases by $V=IR$, but I really find some difficulty in understanding this at the atomic level (what happens with the electrons inside that wire). I ...
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910 views

Why is there an electric field in a wire even though it is a conductor?

If you take a perfect conductor, there cannot be a field across it since if there were, the particles would arrange themselves in a way to cancel out the field right? Yet, why does the same not hold ...
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Why current of a battery drops continuously in high currents?

I have asked this question on EE SE but could not get a satisfactory enough answer. I have shorted an AA battery through an ammeter. Inititially, the current reading on ammeter was around 0.9 amperes ...
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electricity and magnetism [duplicate]

A charge Q is distributed uniformly on the surface of a spherical conducting shell of radius 5 cm.The magnitude of electric field on the surface is 106 V/m. What is the magnitude of electric field20 ...
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31 views

Corona discharge leading to hexagonal structure

Hexagons appear many times in nature, and I'd like to know why they appear in this situation too. Somebody has already been kind enough to help me figure out why this phenomenon occurs - it is due to ...
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52 views

What is Electric-flux?

I've searched the question in the forum, and found the following conclusion : - "In electromagnetism, electric flux is the rate of flow of the electric field through a given area. Electric flux is ...
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What would be the capacitance of an unequal charged capacitor?

I searched for this question but I cannot get satisfactory answer. Say if we have a parallel plate or cylindrical capacitor and if I supply unequal charge to it how could I find its Capacitance. We ...
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52 views

How does electric potential relate to charge density in a wire?

Lets say we are talking about a wire with resistance connected to a battery. How is the charge density, taking into account bound and free charges, at two points connected to the electric potential ...
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89 views

Why is electric flux zero if my point charge is outside of a sphere? [duplicate]

I am currently studying Gauss Law and Electric flux , during one of my exercises they ask me to find the electric flux of a sphere with radius 5 cm and my point charge is 10 cm to the left of the ...
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Simulate Band Bending and Band Alignment in Semiconductors

Are there softwares (simple ones preferred) where we can simulate the band alignments and band bending of a p-n junction, where we can vary properties of the junction materials such as carrier ...
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430 views

comparison between current and voltage sensitivity

Current sensitivity of 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,NAB is ...
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157 views

Is there mechanical strain on a wire along the direction of current flow?

The (attractive) magnetic force on two parallel wires can be seen by the two wires bending towards each other. This can be explained by the Lorentz force acting on the charges and the charges ...
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53 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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72 views

Flow of electrons in an open circuit

In a closed circuit, electrons flow from negative electrode to positive electrode. In an open circuit, electrons only flow up to the end of the circuit. Why don't the electrons keep flowing into the ...
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44 views

Conductive Rod in a Magnetic Field [closed]

I have a question about induction. Imagine a conductive object being moved in a magnetic field. What forces will it experience and how does the induced current in the object affect the motion, will ...
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34 views

Retardation on a Conducting Object in a Magnetic Field [closed]

I cannot solve this question and I need help to understand the physics. The picture below says it all. What is the retardation (negative acceleration) on the conducting object with a mass of 2.5 kg's ...
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137 views

Why do electric pickles only glow at one end?

The electric pickle is often used as an example of a non-ohmic resistor. In the experiment, electric current excites the sodium ions inside pickle, producing very bright and intense light effect. What ...
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53 views

Why does grounding yourself prevent feeling a static shock?

Sometimes I get static electric shocks when I touch certain metallic objects. However, I seem to be able to prevent this by grounding myself by first touching that object with a small piece of metal, ...
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22 views

Analogy of Faraday Cage?

Can we think that an ideal conductor is a friction less space for electrons since under influence of electric field they create an exactly opposing field and produce shielding effect ?If so then how ...
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30 views

If I pass light through a conducting ring will I get an emf induced in the ring? Also if I do get an emf would that not violate energy conservation?

Here is what I think should happen. Light being an electromagnetic wave should have an oscillating magnetic component which should constantly change the flux linked with the conductor. Hence an emf ...
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73 views

Attracting lightning with an ion beam

Can an ion beam be strong enough to create a path for lightning to travel to the ion machine? This is what I found in a lab that may help: An ionization factor jτi (the product of electron beam ...
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26 views

Resistance used to get maximum illumination with proper security

In which way a resistance is to be connected with a bulb labelled 120V-60W when it is connected with 220V DC source so that maximum illumination with proper security is maintained? What is the ...
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33 views

High voltage arc stability reasons (in some cases shape of the arc is rapidly changing)

When turning off 500kV switch we can see an arc like on this picture this arc is very unstable, curved, distorted. It consists of many little loops. While on this picture electric arc patiently goes ...
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29 views

Current in a short circuit [duplicate]

Well,if theoretically we say the value of a resistor is zero then will there be any heat dissipation across the resistor(because heat is produced only when there's a resistance to the flow of ...
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21 views

Why are negative temperature coefficient thermistors accurate for measurements of low temperatures?

Why are negative temperature coefficient thermistors accurate for measurements of low temperatures? How does higher resistance at low temperature accurately measure the temperature?
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79 views

Why do coal power stations not directly use combustion to turn the turbines?

Why do coal power stations run by creating steam rather than from the expansion due to combustion? I understand that in order to generate electricity in a coal power plant, steam is usually produced ...
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48 views

Earth as a conductor

In a lightning rod or other safety devices, charge is directed towards the earth. How the surface of the earth can be used as a conducting path despite being composed of material that is not a good ...
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50 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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26 views

Electrons and ionization in an electric current [closed]

Conductors have free electrons to roam, but is that equivalent to continuous ionization of atoms in a conductor, say when an electric current is running through?
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45 views

What is exactly the “negative” charge?

If we take a particle, a non neutral one, we know we can measure a distribution of charge on it. Now, the fact that this particle may have positive distribution of electric charge it's ok. Maybe ...
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37 views

How to collimate the LASER light using an electric field? [closed]

The He-Ne laser beam is passed through electric field plates. What is the mechanism occururing there and the principle of LASER light interacting with electric field?
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58 views

Voltage and Energy in a capacitor [duplicate]

Well, my first question is related to the energy of the capacitor. Why does the energy of capacitor equals $E=\frac{1}{2}QV$ and not $E=QV$;in other words, why we multiplied it by $\frac{1}{2}$?? My ...
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Can sugar be affected by a magnetic field?

While I was making a morning coffee at work, some sugar from the spoon started to fly away, seemingly towards some foam cups. Can this be explained by magnetism?
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75 views

Resistor and voltage drop [duplicate]

I know that a voltage drop of a resistor is the energy lost from the potential energy of the electrons.well, what i am really confused about is why the potential energy of the electron decreases as it ...
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54 views

Definition of electric current

As I am taught in school that electric current is the flow of electrons, but in some places I faced another definitions like transfer of energy between electrons. I thought that it is the transfer of ...
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129 views

Can pulsating DC current be transformed?

Since pulsating DC current is changing, why doesn't it induce a changing magnetic flux in the transformer core? Is it able to induce a transformed current in the secondary coil?
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160 views

What is wavelength of electric field generated in a wire? [closed]

I read link given below: http://en.wikipedia.org/wiki/Speed_of_electricity Above link says _The speed at which energy or signals travel down a cable is actually the speed of the electromagnetic ...
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50 views

Does the current in a resistor depend on the speed of electrons?

If the speed of electrons in resistor is slow, then will the current be slow and if the speed of electrons is fast, then will the current be fast? Does the current in a resistor depend on the speed of ...
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29 views

Working of electric-tester [closed]

How does the circuit gets completed when we put an electric-tester glow when we put it in the +ve terminal, when actually the electrons flow from the -ve terminal ?
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122 views

Why does the frequency of a Transformer not change?

I was reading about the transformer, when I came across a note by the author that stated that the Frequency is not changed as the flux linked to the secondary coil in a transformer changes. Is there ...
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How does a wire carry alternating current?

Consider a simple network of a bulb whose two terminals are connected to two wires with open ends A and B respectively A o--------💡--------o B Now if a DC ...
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65 views

What is the voltage in this circuit? [closed]

Attached is an image of circuit diagram for which I was asked to calculate the voltage for. However, because of the lack of information provided I belive this is impossible. Am I correct?
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Constant charge in special relativity

We had special relativity introduced in our course and used it to derive some facts. At one place we used the fact that if in frame of reference $U$ the electron has charge $e$, then it also has ...
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What does it means to say an electric charged person has a higher potential voltage compared to the door?

I'm studying electric potential energy and its defined as the energy needed to move a charge inside an electric field from a point $a$ to $b$. Then, it defines electric potential energy per charge, ...
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909 views

Will a bulb glow brighter if voltage is increased but current remains the same?

I understand that increasing voltage increases the energy given to each coulomb in the circuit, so in theory more energy given to a bulb should make a bulb glow brighter. But also if voltage is ...
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190 views

How electrical energy is transfered trhough a wire, and what's flow of charge?

I've read these texts about misconceptions about electricity. This is my understanding: Electrons do move, mut slowly and randomly. What happens is that, in fact, they're just 'conducting' the ...
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175 views

Why do metals become insulators when oxidized?

I don't know the connection between how forming a new bond with oxygen then changes the density of states to transform the metal into an insulator. It seems like a very powerful transformation.
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47 views

Does the alternating current “move” such that there can be Lorentz force present on the wire?

As in question, does the alternating current "move" such that there can be Lorentz force present the wire? Becuase the current alternates on a fixed place there can be no Lorentz force?
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32 views

how the current steadily flows due to motional emf?

In motional EMF, the positive charges (current) flows from higher to lower potential. If this is the case, then the current should stop at the point of lower potential. But this does not happen - the ...
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139 views

How does an ammeter in a circuit work?

Apologies for this simple question, but I'm having trouble grasping the concept of how an ammeter works. Taking the following circuit as an example: When the switch is closed, current flows ...