# Tag Info

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If you press a pile of carbon particles together to form a pill-like disc, you will find that the electrical resistance of the pressed disc is higher than that of a similarly-sized disc of solid carbon. This is because those particles of carbon are not all in good contact with one another. If you then compress that disc, you mash the particles together ...

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A similar question might be why doesn't the air drag on a sky diver push them back up higher? When the skydiver leaves the plane, air drag is minimal. Gravity accelerates them downward. As they fall faster, drag increases until it has a magnitude equal to gravity and acceleration stops. The diver is at terminal velocity. The force of the drag stops ...

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Am I missing something? Yes, you are missing what is held constant in each case. Ohm's Law: I=V/R. Increasing voltage increases current. Should read “Increasing voltage increases current for a fixed resistance.” Power Law: P =𝑉∗𝐼. Increasing voltage decreases current. Should read “Increasing voltage decreases current for a fixed power.” The two ...

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This happens not so much due to the fact that thermal expansion is not linear in temperature (you'd have to be either working with a very cold wire or else operating over very large temperature differences); it has more to do with the fact that when you apply a voltage across a resistance that object's equilibrium temperature is not linear in the applied ...

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Lets make clear from the beginning that Physics theories use mathematics as a tool, imposing extra axioms called postulates, principles,laws so that those mathematical solutions are picked that fit measurements and observations and also, very important, predict new phenomena which become validated. Electricity and magnetism were slowly defined and measured ...

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Assertion A is correct. A short circuit can result in the release of a large amount of energy in the form of heat. That, in turn, can ignite materials and cause a fire. What prevents wires from short-circuiting is the separation of the conductors by electrical insulation. In the case of wires it's the insulation on the surface of the wires. Most ...

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Your interpretation makes intuitive sense, because you're assuming that $v$, the drift velocity of the charge carries, is the same at all points along the wire. That assumption isn't right. Water flowing through pipes (or a river) is a common analogy: A wide spot in the conductor is like a wide tank that the pipe runs into one end of and out the other end ...

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increasing the gas pressure increases its density, which decreases the mean free path length of moving ions. This limits the distance an ion can travel before it gets deionized in a collision, and increases the amount of electric field strength required to achieve a breakdown cascade.

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As the others say, you are implicitly holding one factor constant and seeing how the others are related but a different constant factor in each case. A real world example may help. Consider an old style filament light bulb. It is intended to be used in a $220V$ country and consume $110W$. So, it should draw $0.5A$ and needs a resistance of $440 \Omega$. ...

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Materials in our world are made up of atoms. Atoms are made up of different particles, one of which is electrons. Electrons can be made to jump from atom to atom inside a material. An electric field is the force that pulls electrons. Electricity is the movement of electrons in an electric field. The measure of how fast the electrons are moving is called ...

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Analogy Think of water running through a pipework: it may run faster where the pipes are narrower, and slower in the wider parts, but the quantity of water which enters is the same as the quantity of water that exits. There may be temporary decompressions here and there, but the water eventually has to come out, unless there is a leak or a reservoir ...

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Current in a series circuit are the same everywhere, but when there is a bulb creating a potential difference, wouldn't the rate of the same number of electrons flowing, coming out from the bulb change...? Perhaps the following will help clarify things. The bulb does have an affect on current. The rate of electrons flowing (the current) in the series ...

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Now since we always get an equal and opposite voltage across the inductor for each change in source voltage so it means that the current will never be able to flow in the inductor . . . . This is a common misconception. For the inductor to generate a voltage $L\frac {dI}{dt}$ the current must be changing ie $\frac{dI}{dt}\ne 0$. So if the currents ...

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The varying magnetic field around the coil partially resists drift current and every 2/f sc (starting from 4/f sc ) it actually helps it.

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It depends on where the resistance is. If it’s in the wires between the source and the inductor then the answer given by @Dale applies. If it’s the resistance within the coil then the answer given by @Vilvanesh applies. If it is distributed between the wires and the coil you would need to specify the amounts to determine the voltage across the coil and its ...

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You mentioned that there is resistance in the circuit, but did not draw it. I will assume that you intend the resistance to be in series with the inductance. In that case we can treat the circuit as a simple voltage divider using complex impedance. The impedance for the resistor is $Z_R=R$ and the impedance for the inductance is $Z_L=j\omega L$. Putting ...

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Both the voltages have to be out of phase by $180^o$. This comes from Kirchoff's law. V + $V_L$ = 0. Therefore V=$-V_L$ This holds good even if there is no resistance for the inductor.

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Yes. These are measurements of energy because energy equals power (measured in kilowatts) multiplied by time (measured in hours). The total energy wasted is simply the sum of the wasted energies for every 15 minutes because energy is a scalar.

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The maximum theoretical power that a turbine can develop in the absence of any efficiency losses is given by the product of the mass flow rate through it times the pressure drop across it, taking care of units. Any real-world turbine will deliver less than this. This means that without knowing the pressure drop or the flow rate, no estimate of your turbine'...

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My textbook says, that across a battery or a cell there should be a potential drop equal to its e.m.f. To be clear, you textbook is referring the potential measured across the battery terminals without any circuit connected to the terminals, i.e., the no load or open circuit potential across the terminals. Now I've also learnt from sites that the ...

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across a battery or a cell there should be a potential drop equal to its e.m.f. Sometimes called the "open circuit voltage", this potential only exists when there is no current flowing through the battery. Internal resistance within the battery will reduce that potential as current increases. I've also learnt from sites that the potential at all points ...

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The electric field created by the anode is too weak to significantly influence the emission of the electrons from the cathode, which is mainly due to thermal effects, hits by the gas molecules, electron repulsion among themselves, etc. However, once the electrons are released from the cathode, they do feel the anode field and start accelerating towards the ...

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It does as others mentioned. For example, suppose you have a source with two poles, one pole being at potential 0 (zero) and the other one at a value V. if you insert two resistors in series between the two poles, with resistance R1 and R2, the current in the circuit is I = V/(R1+R2). There is a potential drop of V1 = R1 I across the first resistor and a ...

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In a word, no. The fields pass through each other, although they may interfere with each other along the way. Electromagnetic radiation is like light; if you take a flash photo in even a strongly-lit room, your subjects will still be blinded by the flash.

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