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The Kelvin temperature scale is an absolute temperature scale. That is 0 K is absolute zero. It also has the property that temperature intervals on the Kelvin scale are the same as on the Celsius scale. That is a decrease or increase of one degree Kelvin is the same as a decrease or increase of one degree Celsius. To meet these two requirements it is ...


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EV stands for exposure value. The equation to convert EV to lux is: $$ L = 2.5 \times 2^{EV} $$ Since you're using a Sekonic meter note that Sekonic provide a conversion chart here.


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The Weights and Measures Act (the origin of the Imperial Units) does not speak of temperature. It was intended to create a uniform system for trade. You don't sell temperature, in the way you sell a pint of milk or a yard of cloth. And frankly, when it was first conceived (before Magna Carta, which already stated: "There shall be but one Measure ...


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According to the wiki page on Imperial and US customary units Fahrenheit is part of both the Imperial and US customary system. I can't think of any reason it wouldn't be included in the Imperial system. Note that in the wiki page on Imperial units it is mentioned that the weight's and measures act (which defined the Imperial system) explicitly used the ...


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The first formula is written in the Gaussian unit system, while the second one is in the SI system. In the Gaussian system, the unit of electric charge is $statC =g^{1/2}cm^{3/2}s^{-1}$. So, the Sommefeld parameter in the Gaussian unit system is dimensionless as it would be.


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Motion. Velocity is obviously relative, and no "absolute rest" frame is known to exist. Even acceleration, which is in a sense absolute, is sometimes specified relative to a local inertial frame (ie. freefall), sometimes relative to the distant stars (so you can talk about the acceleration of astronomical bodies due to gravity), and most commonly in ...


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Height / altitude. From Wikipedia: Indicated altitude – the altimeter reading Absolute altitude – altitude in terms of the distance above the ground directly below True altitude – altitude in terms of elevation above sea level Height – altitude in terms of the distance above a certain point Pressure altitude – the air pressure in terms of ...


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One that has many zero points is the standard Gibbs free energy of formation: each element has their own zero point.


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Gauge pressure. From Wikipedia: Gauge pressure is zero-referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure.


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Gravitational potential energy (in a constant gravitational field such as near the Earth). This is the usual scenario in elementary questions for high-school students. One may use the starting point of a body as zero or the end point or the ground.


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Another example of an arbitrarily selected zero point is longitude. This was not always measured from the Greenwich meridian - Paris has been used, and the ancient Greeks (Ptolemy, specifically) used an island believed to exist off the west coast of Africa* in order to avoid dealing with negative numbers. Really, though, none of the examples anyone have ...


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Luminosity. The Magnitude of a star is a logarithmic scale with an arbitrary zero point. In SI unit of brightness is the Candela or or there is luminosity if direction is not accounted for. From Wikipedia: In SI units luminosity is measured in joules per second or watts. Values for luminosity are often given in the terms of the luminosity of the ...


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The scale used to define positions on a highway depends on the point chosen for the Zero Marker. There is a difference between defining a position on a highway, like Mile #25 or Exit 125, and a distance on that highway: it's 30 km from Km 15 to Km 45. The same thing is true in temperature scales, where we need to distinguish between labelling a position ...


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Sound can be measured in deciBels ($\mathrm{dB}$) but also as an intensity measured in $\mathrm{W/m^2}$. $0\,\mathrm{dB}$ on this scale is equal to $1\times10^{-12}\,\mathrm{W/m^2}$.


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Time, in which case each system's zero point is often called its epoch: http://en.wikipedia.org/wiki/Epoch_%28reference_date%29


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You are correct. If you worked through the same steps on the distance ladder in a universe with a different speed of light, you would find the answer in light years would be different. Your question on whether light travels one light year in one year, though trivial sounding, opens the door to difficulties that are inherent in the nature of space-time. Your ...


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The kilogram-force is not a standard unity: The kilogram-force (kgf or kgF), or kilopond (kp, from Latin pondus meaning weight), is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a 9.80665 m/s2 gravitational field (standard gravity, a conventional value approximating the average magnitude ...


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$N=CV/m$, hence your solution turns into $\frac{C}{m}$, which doesn't look right (electric field in V/m = force in N / charge in C) I suppose, that answers your question. You can use Wolfram Alpha for unit conversion, for example in your case. And here you'll see how force relates to voltage: ...


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I have a torque wrench which reads in kg•M, but it actually displays kilogram-force • meters. The kg-force is the weight of one kg in one gee. Thus, 9.8 N•M = 1 kgf• M. Using kg as force is not SI, but is rather common.


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This depends on your system of units, but in general the answer is No. Electric charge is a fundamental physical dimension and its units can only be reduced to combinations of mass, length and time via a suitable requirement of dimensionlessness on an appropriate constant. In particular, if the system of units you're using has a dimensionful permittivity of ...


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When I wrote a units package, I put degFinterval and degCinterval as units, specifically units that are intended to be squared and multiplied and divided. I put "interval" in the name to make it absolutely clear to users that they should only be multiplying temperature differences (which don't have a fixed origin) rather than raw temperatures (which do). (In ...


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It greatly depends on what you need to do with your temperature. In almost all physics applications, the thermodynamic temperature is the only one that is meaningful. A notable exception is in linear heat flow simulations, where temperature differences only are important (e.g. between a point in the simulated region and the "ambient"). The squared ...


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If you are using an absolute temperature, you should use Kelvin. For instance, when using the Stefan-Boltzmann Law, $$P=A\epsilon\sigma T^4$$ it wouldn't make sense to have units of $^\circ C^4$; only units of $K^4$ physically make sense here. However, if you are using a temperature difference, then both Celsius and Kelvin are equally valid because a ...


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The symbol kW(e) or kW${}_e$ refers to the "kilowatt electrical". It is the part of the power that is actually used by the devices connected to the power station or the grid, effectively the average of $P = U\cdot I$. The "kilowatt electrical" should be contrasted with "kilowatt thermal" i.e. kW(th) which represents the power including the thermal losses. So ...


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Very cryptic way to write units, but it can be decrypted: da.Nm= decaNewton.meter (http://www.deprag.se/omvandlare.pdf) M.KGS=meter kilograms (http://www.thetoolhut.com/Torque-Conversion-English-Metric-Ft-lbs-M-kgs.html)


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The unit $^\circ\mathrm{C}^2$ does make sense. It represents a difference in temperature squared. You are worried that it is invalid because the origin is shifted. This is not a problem though, because we use $\mathrm{m}^2$ all the time, and there is no natural origin at all for positions.


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One never pluralizes unit abbreviations. Your link goes to the BIPM, the body responsible for maintaining the definitions of the international system of units, and is authoritative. The folks at NIST agree and address most of your questions. I would say The pipe is 0.75 m long. or The pipe is 75 centimeters long. or even The pipe is ...


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cms and kgs are wrong. The SI units are abbreviations which are also used in the plural. You will write 2.6 m/s or 1 m/s, but say "2.6 meters per second" or "1 meter per second" respectively. Keep in mind the SI units are also used in tons of other languages that do not form the plural by attaching an -s. The units look the same in those languages. (e.g. ...



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