New answers tagged

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There is no limit on the 'ability to store charge' involved. What is different, is the proportional relationship between stored energy per unit charge (voltage) and amount of charge (ampere-seconds) stored. A rechargeable battery keeps its charge chemically bonded (and stores a LOT of charge for a given voltage rise), while a close-spaced-plate capacitor ...


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A typical voltmeter contains an internal Ohmic resistor with known and very high resistance $R$ (called the "input resistance" or "input impedance"), and an extremely sensitive ammeter that measures the current through that resistor. When the voltmeter is connected in parallel across some circuit elements, then ideally the internal resistor has resistance ...


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The diagram above has a very important feature. It is the connection between the Earth and the outer conducting shell. Assume that the Earth is a conducting sphere and has some net positive charge on it. This will mean that the outer shell connected to it will also have some positive charge on it but the wire between the outer shell and the Earth means that ...


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So, the potential is not necessarily zero both at the ground and at infinity. First off, there's nothing in physics which forces the potential to be zero at infinity; it just happens to be a nice way to think of the Coulomb potential. Potential energies are not absolute numbers; there is a constant of integration that enters into them! Second, there is ...


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Suppose the e.m.f. is denoted by $V_0$, and the current in the circuit is $I$. Assuming a sign convention such that $I > 0$ when the current is clockwise, the first thing is to write $I$ in terms of $V_0$, $R$ and $r$. In the manner you have drawn the circuit, $r$ is the "internal resistance" of the "battery" whose e.m.f. is $V_0$. Remember, the e.m.f. is ...


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$Q=CV \Rightarrow \frac {dQ}{dt} = I = C \frac {dV}{dt}$ The voltage across the capacitor is equal to the voltage of the supply. So whatever the voltage of the supply does the voltage across the capacitor exactly follows. At time $t_A$ the capacitor is uncharged and the voltage across the capacitor is zero. However at this time the voltage of the supply ...


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Alternating circuit voltage and current periodically reach their respective maximum values after a certain time interval. Consider the current I=I(m)sin(wt) and Voltage V=V(m)sin(wt+pi/2)= v(m)cos(wt). What this phase difference signifies is that if you start the circuit at t=0, then the voltage at t=0 v=V(m) while i=0, meaning the circuit will gain maximum ...


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The 6V in 6V battery is a label which gives an indication of the sort of voltage which might be obtained from such a battery. For example if your ^ V battery was an lead-acid battery and it was fairly new and fully charged its voltage would be 6.3 volt and if older or partially discharges then it is more likely to be 6 V. A 1.5 V alkaline battery at the ...


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EMF or Terminal voltage will be considered same if battery has no internal resistance. If battery has some internal resistance then terminal voltage will be different(less) from the EMF or potential difference from the battery. If a battery has internal resistance then what will be considered if the same statement is given.


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In your questions all the cases are assumed to be ideal unless mentioned. Therefore the electromotive force and the terminal voltage are equal in that case as internal resistance of the battery is considered negligible(if not given) . If the battery has internal resistance then the emf remains constant,but the terminal voltage decrease by a value which is ...


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in series the current is the same through each resistor. Not just the same, the current through each is identical. So that the lightbulbs will all have the same brightness but dimmer than if there was just one bulb on there. Well of course, series connected resistances add and so, the total resistance of two series connected bulbs is greater ...


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Light bulbs, or any loads, in series will all have the same current. This is unrelated to Ohm's Law - it's Kirchhoff's Current Law and it applies if the loads are ohmic or not. Assuming your source voltage stays the same, adding bulbs in series will increase the total resistance which will decrease the total current and make all the bulbs dimmer. The ...


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I can't understand at all everything after "As the resistance increases ...". Is that really how it was explained? Nonetheless there's an interesting point here. The analysis is not exactly the same as for an ohmic resistor, but not for the reason you suggest. The thing to consider is that the resistance of the light bulb depends on the temperature ...


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You are correct that light bulbs are non-ohmic (they don't obey Ohm's Law). But that makes no difference. The same current flows through each, even if they have completely different resistances. Electrical current (charge per second) is like the flow of a river. If there are no leaks, and no tributaries joining the river, then the volume of water per ...


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If voltage is all that you know, then the answer is No. If you know how much charge $Q$ in Coulombs is added, you only have to divide by the charge $e$ on each electron (in Coulombs). Otherwise, if you have a parallel plate capacitor and you know the capacitance $C$, you can work it out from $Q = CV$. Your suggestion that the extra electrons 'push more' ...


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Within a battery a chemical reaction is responsible for moving mobile electrons from one terminal to the other. The terminal from which the mobile electrons come from is called the positive terminal (deficit of mobile electrons) of the battery and the one that they go to is called the negative terminal (surplus of negative electrons). If there is no ...


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I would say it is both! Because of the abundance of electrons, the electric field at the battery pole/boundary, at the instant of turning on the switch (t=t0), is quickly (within a few Debye lengths) screened and cannot possibly reach the electrons further down the wire. However, the electrons at the vicinity of the pole that do feel the effect of electric ...


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It is not generally realised that "internal resistance" is a myth which cam be evaluated only by practical experiment and calculation using Thevenin's theorem. But that does not mean that it is a useless concept. Indeed it is essential for design in ALL branches of engineering. For example a plumber measures the efficincy of a water-supply by measuring ...


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UPDATE : John : Thanks for data. Graph is ok. I note your intercept is E=3.94V but your calculations use E=4.5V. This explains the discrepancy in your results. If you use 3.94V you get r ranging from 1.59 to 1.76, close to slope value of 1.68 Ohms. ORIGINAL ANSWER : Your line of best fit gives an average internal resistance r based on all measurements. ...


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A power station or generator is not the thing you are asking about here - Your main question is why 25kV is the output. When designing a power station an engineer tries to get the most power out of the system as possible for a given input of energy, or peak efficiency. After the generator distribution and use becomes the main concern. It tends to be the ...


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The generators in power stations consist of coils rotation in a magnetic field produced by an electromagnet. Some of these electromagnets are energised by the generator itself but the larger generator have a smaller generator associated with them to provide the current which passes through the electromagnet. The induced voltage depends on the magnetic ...


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The definition of resistance of a component is $\text{resistance of component (R)} = \dfrac{\text{potential difference across component (V)}}{\text{current passing through component (I)}}$ This is not Ohm's law it is the definition of resistance. It so happens that for some components it is found that $V \propto I$ which is called Ohm's law. This is an ...


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I'm not sure exactly what you're asking for. But let's say there's an electric current flowing through a straight wire segment of length $l$, then the change in $\Delta\phi$, or $V$, would be defined by $$\Delta\phi = \int \mathbf{E}\cdot d\mathbf{l}$$ Because it is a straight wire, $$\Delta\phi = E\cdot l$$ But we have a definition of current $$I = ...


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Georg Ohm's original experiments, 1825, established that for a set temperature, the current through a specific length of a conductor was proportional to the potential difference applied. Ohm's law is empirical; it cannot be derived directly from Maxwell's equations as it depends upon material properties. It is violated by many materials, and even then ...


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The first thing to note is that you must never use the word voltage unless you are sure that you and your audience are aware of the fact that is shorthand for “a difference in voltage” or as you have used “voltage drop”. I would prefer to use the term “potential difference”. All this has to do with energy and a type of energy that a system has which makes ...


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You are correct about inserting lightbulbs at X and Y. The same current flows through each branch, so the lightbulbs will be equally bright. However, the question is not whether there is a difference in the currents flowing through X and Y, but whether, if you connect a wire between them, any current will flow through it. Your objection, of course, will ...


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What is the difference between the potential difference and potential energy of an electron? If I understand your question right, these terms are describing the same thing - one is just in a "per charge" version. Electric potential energy $U_e$ is the potential energy associated with one spot in the circuit. Electric potential or just potential $V$ is ...


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Batteries are made up of one or more electrochemical cells, arranged in series. In these cells an electrochemical Redox reaction takes place: $R+ze^{-} \to R^{z-}$ $O-ze^{-} \to O^{z+}$ Where $R$ and $O$ resp. are a reducing agent and oxidising agent. This transfer of electrons provides the EMF of the cell. As more current is drawn from the cell, the ...



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