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# ev - ΔE = 1.60e-19 J ∴ 1eV = 1.60e-19 J This number is...

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Electron Volts The Joule is a very large number for dealing with the energies of electrons, atoms, and other small objects. You probably noticed in previous lessons that it was not uncommon to have numbers of the magnitude 10 -18 J. Quite often physicists use units that are better suited to dealing with the measurements they are making. It’s the same as when you talk about “5 dozen eggs”… it is more convenient to think of it this way instead of as “60 eggs”. For this reason the electron volt ( eV ) is used. It is defined as the energy one electron gains by moving through a 1 V of potential difference. We can calculate how many Joules this is equal to… ΔE = qV = (1.60e-19 C) (1 V)
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Unformatted text preview: ΔE = 1.60e-19 J ∴ 1eV = 1.60e-19 J This number is on your data sheet of you ever need it. Example 1 : An electron is moved from positive to negative through a potential difference of 1000V. How much energy did it lose in electron volts? 1e- (1000V) = 1000 eV Wow, that was done quick! I could’ve done that calculation in my head. This equals 1.60e-16J (see if you can confirm this). The electron volt is NOT a metric unit. • It is so common, though, that we still need to recognize and understand it. • Remember to always change your energies into Joules before sticking them into the formulas, otherwise you will get the wrong answer. 10/31/2005 © studyphysics.ca Page 1 of 1...
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