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How many volts are needed to give an electron 21 eV to escape metal?

In summary, to give an electron 21 electronvolts (eV) of energy to escape from a metal, a potential difference of 21 volts (V) is required, as 1 eV corresponds to the energy gained by an electron when accelerated through a potential difference of 1 volt.
  • #1
nif
If an electron needs say, 21 electron volts to escape a lump of metal, and that lump of metal is connected to a power supply... how many volts would be needed to give the electron at 21eV that it needs to escape?And how do you work it out...?cheers, nif
 
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  • #2
What you're hinting at here is the photoelectric effect, I think. If an electron needs 21 eV to escape, then a 21 eV photon can just edge the electron out of the metal. Connecting a power supply to a piece of metal sets up a static electric field inside the metal, and the EM force is mediated by photons. Of course, simply connecting a power supply to the metal does not guarantee that you can ionize it, because you can set the field up so that the electrons run around the circuit.As for how you determine the voltage of the power supply, an eV isdefinedas the kinetic energy acquired by an electron when accelerated through a potential difference of 1 Volt. So, for electrons21V-->21eV of KE.Tom__________CountdownTom will be 30 in47
 
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