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6

First, there is nothing wrong with our charge polarity conventions. They are predict electrical phenomena just as accurately as the opposite convention would have done. Did we have a problem if since the begin of their discovery we called them positive particles and negative to protons? We could predict the behavior of electrical phenomena equally ...


3

To simplify, let's think of a prismatic volume, as if a planar figure (in $xy$ plane, area $A$) had been extruded in $z$ direction. Let's assume that conductivity ($\sigma$) is dependent on $x$ and $y$, but not on $z$. And let $L$ be the prism length in $z$ direction. We want to compute total resistance between both ($xy$) parallel faces. If we take a small ...


3

Your answer : The bowlers and fielders rub the ball to make the ball smooth and shiny on one side and leave it rough on the other side. To generate reverse swing. There is a lot of science behind swinging the ball. The ball gets reverse swing when it is quite old and you see not only the bowlers but the fielders as well rubbing the ball before every ...


2

Resistive Filament - Voltage vs. Current If you referring to measuring the $V(I)$ dependence of the heated filament I would derive an approximate equation as follows. $T: \textrm{Temperature of the filament}$ $P_{dis} \equiv V \cdot I: \textrm{Power dissipated}$ $k: \textrm{Coefficient of temperature vs power}$ $R \equiv V/I : \textrm{Ohmic Resistance}$ ...


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One of the problems with doing experiments on static electricity is that the static charge can leak away while you're trying to do your measurements, and one of the main ways the charge leaks away is due to humidity of the air. I don't know what the humidity is in Kolkata, but I would guess that it's much higher during the monsoon that it is during the ...


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A battery is no capacitor, and the actual charge stored in the battery terminals is very low. When you connect the anode of one battery to the cathode of another, that charge is transferred very quickly, and the voltage drops to zero. When you connect anode and cathode of the same battery, a chemical reaction takes place, and charges flow inside the battery ...


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Specifically, you can ask any wire to get equally "hot", but since different materials have different melting points, some are better-suited for heating elements. In electronics, heat is a by-product and is unavoidable. Most components generate a more-or-less fixed amount of heat "per second" in the silicon. The plastic that microchips are encased in is ...


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What you describe essentially happens in superconductors. There "perpetual electricity" exists in the form of super currents. In normal inductors, though, the resistance of the conductor steadily dissipates the current leading to field collapse.


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An electric current is the flow of electric charge. But electric charge is not an entity, it is a property that must be 'carried' by a charge carrier. An electron current, the flow of electrons, contributes to an electric current since the electron 'carries' negative electric charge. However, an electric current is not necessarily an electron current. ...


2

Exactly what is this "circuitous route"? Does the thing I touch also have to be touching the carpet? Though I'm not a native English speaker I am pretty sure that a circuitous route is a path that combines you shoes and the carpet as were they a part of a circuit. The thing you touch has to be connected to the carpet (by touching the carpet itself or ...


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(Moving this from my comment to an answer) Yes, the electric field simply penetrates the glass wall and charges (the electrons) placed in that field will feel a force and move. The glass does not really interact with the charges on either side, so you might as well remove it completely (theoretically).


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The formula that you quote from the online is correct if the curve is a circle, i.e. the radius is constant and one calculates the magnetic field in the middle of the circle. Your formula uses the same assumption because you also took radius equal to $R$, i.e. $$r_s=Rcos\phi \ \hat{i} + Rsin\phi \ \hat{j},$$ but there are some mistakes: 1) $\text d \vec ...


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Higher voltages allow conduction paths that can do less than kill. You can get serious electrical burns and even arcs that pass through the body and leave burn channels, as in lightning strikes, or sitting on a charged laser capacitor (fatal for a Stanford grad student many years ago). Nerve damage and permanent heart arrhythmia can result. Might be good for ...


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Both the uses are correct. Charge density may be uniform or may vary depending on its position making it a function of $r$ and hence $\rho(r) $ It just depends upon how the charge is distributed in the region.


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There are a few key bits of physics and math to understand here, but one does need to be very careful to avoid producing a circular argument. The key, concept I think is that of a linear circuit element, for which the output is precisely proportional to the input. The precise meaning of 'input' and 'output' depend on the precise device, but this does ...


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We do! (Or at least, we should, to be complete.) Imagine the basic arrangement of a bar magnet, north up, moving upward toward a solenoid. Faraday's Law has a very important negative sign for this question, which dictates that the new current generated by this increasing flux is going to be clockwise from the top (use the right-hand rule, and flip it for ...


1

The electron gun produces electrons by heating the cathode; this shakes out electrons from the metal ("boils them off"), and as soon as they're out, they are repelled and accelerate away to do your bidding. This is called Thermionic Emission. When an electron is emitted, another one comes in from the cable connecting the cathode to the power source. The ...


1

When they say "Do not ignore electric force", they mean that there is both a magnetic and an electric force on the electron/positron, and you should not forget the electric force. In other words, you are asked to compute, for the $\vec v_+$, $q_+$ of the positron, the effect on the electron of its $\vec E$ and $\vec B$ field. Fortunately, 5 keV (kinetic ...


1

The rest mass of an electron is 0.511 MeV. When an electron and a positron annihilate their mass turns to energy (two 0.511 MeV photons) so for each annihilation an energy of 1.022 MeV is released. One electron volt is $1.602 \times 10^{-19}$ joules, so in joules the energy released is $1.637 \times 10^{-13}$ J. You ask what happens if $2.3 \times 10^{28}$ ...


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For a capacitor with closer plate spacing (all else being equal), the electric field in the dielectric between the plates is stronger. Assuming a uniform electric field, the potential difference is given by the product of the spacing and the strength of the electric field: $$\Delta V = E\cdot d $$ So, the potential difference can be the same for both ...


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I'm sure the intention of this question was to test your understanding of charging by induction. The assumption of the question is that the wet filament would be a conductor and the dry filament an insulator. The positively charged rod attracts negatively charged electrons. Electrons will move through the wet filament onto the sphere. When the filament ...


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The apparent brightness of an incandescent bulb is a very strong function of the temperature of the filament, because it behaves approximately like a black body. Thus, much of the power emitted will be in the IR. The black body spectrum for different temperatures can be found, for example at wikipedia: Note this is a visual representation of Planck's law. ...


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Would the human start emitting photons and die? EDIT: This answer is an answer to the original question regarding "a billion" positions. The question was subsequently edited to now read "2.3*10^28" positrons. That is not cool. The human would start emitting photons. This is exactly what happens during a PET (Positron Emission Tomography) scan at your ...



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