How can i find the Potential difference?

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Homework Help Overview

The discussion revolves around calculating the potential difference required to accelerate an electron from rest to a speed of 0.99c. The problem involves concepts from electromagnetism and relativistic physics.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to use the equation relating energy and potential difference but questions their calculation after obtaining a different result than expected. Participants discuss the relationship between energy, potential difference, and the relativistic factor γ.

Discussion Status

Participants are exploring the implications of the equations used and clarifying the relationship between energy in electronvolts and volts. There is an ongoing dialogue about the interpretation of the results and the units involved.

Contextual Notes

There is a mention of the potential confusion between energy units (eV) and potential difference (V), highlighting the need for clarity in the context of the problem.

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Homework Statement


Through what potential difference must an electron be accelerate, starting from rest, to acquire a speed of 0.99c?

vf=0.99c(m/s), vi=0(m/s), m=9.11e-31(kg), q=1.6e-19(C)

Homework Equations



E=γmc^2=V*q

The Attempt at a Solution


I plugged in all knowns in the equation and find V(emf).

What i got is 3.63e6 eV but the answer is 3.1e6 V.

What did i do wrong in the progress??
 
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The voltage gives the electron extra energy over its rest energy, mc^2. So Vg=mc^2(γ-1).

ehild
 
But how does (γ-1) come from??
 
ehild, Never mind, i got it!

But should the unit be eV rather than V?
 
The question is potential difference, that is volts. But the change of energy of the electron is the same number in eV as the acceleration voltage: 1 elementary charge times U potential difference is 1*U =U eV.

ehild
 

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