# Tag Info

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There are two main reasons As temperature is decreased the voltage of a car battery decreases and it's internal resistance increases. This means the battery can supply less current. As temperature is decreased the viscosity of oil in the engine increases so the engine is harder to turn over. In the days before fuel injection there was a third factor ...

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In a metal the Fermi energy is somewhere in an unfilled band. At any temperature above absolute zero (which you can never reach) there are states available for electrons to get to and result in conduction at the Fermi surface. This will occur in any metal. Superconductivity is a separate phenomena that I won't touch on here.

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At present, there is a belief (though obviously not verifiable) by solid-state physicists that a metal cannot exist at absolute zero. The Fermi surface of the metal will be unstable to order of some sort such as superconductivity, charge density waves, magnetic ordering, etc. With that said, let us concentrate on your scenario though. If there are no ...

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The drift velocity is the net velocity of electrons in a certain direction under an applied field. The thermal velocity is has no net direction because it is randomly distributed and occurs in any metal at finite temperatures. Since the two velocities are different, it does not make any sense to say they are qualitatively equal, even though you may equate ...

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The voltage differences you can get from thermocouples are usually in the range of $\mu$V per Kelvin for metals. In other materials this can be a bit higher but there is no material that can create thousands of Volts for a temperature difference between the heating and other parts of the building. For static electricity you need a few conditions coming ...

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Current as low as 10mA can paralyze, and 100mA can induce a heart attack. Be careful even when working with "low" currents.

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In order to have the hot side remain hot, and the cold remain cold, while transmitting the electricity, ideally a substance is desired that conducts electricity well, but heat poorly. No. The two ends are assumed to be connected to heat sources or sinks that maintain a constant temperature at those nodes. Heat does flow well from one end to the other, ...

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The thermoelectric effect is the direct conversion of temperature differences to electric potential differences (Seebeck effect) and vice-versa (Peltier effect). When considering the electrical currents and heat fluxes involved, there is a size dependency, but such is not the case for the temperature differences and the electric potential differences ...

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Micro black holes have been hypothesized in some large dimension string phenomenological models and are searched for in the experiments at the CERN LHC. The first approach to the decays was thermodynamic with Hawking radiation diminishing them rapidly. Their lifetimes are very short so there is no way to gather and contain them and experiment with feeding ...

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A Peltier module is not what you want. Some of the specs that I've seen require minimum currents of a few amps (≈2A for a small module), so unless you want to lug around even a small sealed Lead-acid battery with attendant wires, I'd think of something else. In fact, an electrical solution may not even be suitable. However, how about modifying a gas ...

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As mentioned by Programmer, saying that if the wire temperature is constant then half of the heat will flow in either direction is incorrect. It really depends on the boundary conditions on either end of the wire (since it is of finite length). Assuming that the wire is at a spatially uniform temperature (not constant in time) and has same boundary ...

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I would like to know whether Carnot cycle limits every kind of thermal to kinetic/electric energy like thermocouples? Yes, since any conversion of heat into "work" is limited by Carnot, as you said: I know that heat engines (heat to kinetic) are limited by Carnot cycle . Also what is the highest possible efficiency of Carnot cycle? The ...

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H2 + O2 is exothermic. That drives the fuel cell. Platinum adsorbs H2 and O2. This means it "sticks" those atoms to it so that the offering and accepting of electrons is made easier. This presenting of atoms must have an energy cost and so weakens the diatomic bonds otherwise keeping respective H2 and O2 molecules bound. That is why heterogeneous ...

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Why does the platinum take an electron from the hydrogen? Remember that this happens in a fuel cell, where the other electrode loses electrons to O2. The platinum is effectively only an intermediary. It's a metal, so there are a lot of electrons which are not bound to one specific atom. O2 can easily steal one of those, which would leave the platinum ...

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The calibration curve you show isn't typical. In fact there is no typical calibration curve because different types of thermocouples can have very different voltage:temperature dependences. There are lots and lots of articles giving different calibration curves - I selected this PDF as being fairly representative, or try this image search for lots of other ...

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I am not an expert in thermodynamics but I think the following is reasonable: When heat flows from A to B (temperature $T_a$ and $T_b$) then you could theoretically do work - efficiency given by the ratio of temperatures. A Peltier is an inefficient heat engine running in reverse (a heat pump), and I thought the efficiency is the ratio between the work ...

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If you take a length of copper wire at the same temperature, then the average kinetic energy of an electron, and therefore electron density, is the same through out the wire, balancing the metal ion density. The copper wire is electrically neutral at every point on average. Now heat one end. This raises the average kinetic energy of electrons while reducing ...

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Have you heard of superconductivity? This is a phenomenon where a material exhibits zero resistivity near absolute zero: it clearly contradicts your assertion that thermal excitation is needed for conductivity near absolute zero. For a semiconductor, it is true that electrons need to be kicked into the conduction band by thermal fluctuations - but for a ...

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The drift velocity of electrons in a metal is given by the equation $I=enAv_D$ where $I$ is the electric current in the metal wire, $n$ is the number of electron density, $A$ is the cross sectional area of the metal wire and $v_D$ is the drift velocity. From this we get $v_D= \frac{I}{enA}$ The thermal velocity is given by ...

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In a solid body the energy that we call heat is stored as vibrational motion of the atoms/molecules in the solid. When you place a hot solid in contact with a cold one the vibrating atoms in the hot solid bash into the more slowly vibrating atoms of the cold solid and transfer energy to them. You end up with the atoms in the hot body vibrating a bit less and ...

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If you only want to heat the bit to help melt off ice from the screw and do not care about cooling the bit, then the Peltier device, which is a heat pump, is unnecessarily complicated and delicate. The most efficient way to heat something is through a resistive load (i.e. like in a toaster). There are a number options for making the heater, but a 100 Ohm, 1 ...

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