Planck's Constant Conversions: J s to eV s

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Homework Help Overview

The discussion revolves around converting Planck's constant from joule-seconds (J s) to electronvolt-seconds (eV s) in the context of a physics final exam. The original poster seeks clarification on how to perform this conversion given the constants provided in their exam materials.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand the conversion process for Planck's constant, questioning how to relate joules to electronvolts. Some participants provide insights into the definition of an electronvolt and its relationship to joules, while others confirm the need to divide by the charge of an electron.

Discussion Status

The discussion is active, with participants exploring the conversion method and clarifying the relationship between joules and electronvolts. There is a focus on understanding the underlying principles rather than reaching a definitive conclusion.

Contextual Notes

The original poster is working under the constraints of a physics final exam, which includes a specific list of constants but does not provide Planck's constant in the desired units. This limitation is central to their inquiry.

JayBird
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So, my physics final is tomorrow, and for the test we are given a list of constants. On this list is Planck's constant as 6.626x10^-34 J s. Now, that's all well and good, but they don't give it to us in eV s! And we need it in eV s for some of the problems. Given that we also get 1u=931.5MeV=1.66x10^-27kg, is there any way to convert it from J s to eV s? Thanks!
 
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1 eV is an amount of energy required to move an electron over 1 volt potential difference. Since qU = W, where q is the charge, U is the potential difference and W is the potential energy it acquires in respect to the initial point, an electronvolt is (charge of an electron) x (1 volt) = (answer in Joules) (since 1J = 1Cx1V). Therefore, 1eV is roughly 1.6 x 10^-19 J.
 
So I divide it by the charge of an electron? Thanks!
 
Yes. To get joules from electronvolts, you divide electronvolts by the charge of an electron.
 

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