Calculating Electron Velocity with 3eV Energy

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SUMMARY

The discussion focuses on calculating the velocity of an electron with 3 eV of energy, accelerated by a constant electric field of 10 V/cm over a distance of 0.1 cm. The initial energy is converted to joules (4.8E-19 J), and using the kinetic energy formula (0.5 * m * v^2), the initial velocity is calculated to be approximately 10^6 m/s. The final velocity is determined using the kinematic equation, resulting in a final speed of 1.03E6 m/s. The conversion of electric field units from V/cm to N/C is clarified, establishing that 1 V/cm equals 100 N/C.

PREREQUISITES
  • Understanding of kinetic energy equations, specifically 0.5 * m * v^2
  • Familiarity with electric field units, particularly the conversion between V/cm and N/C
  • Basic knowledge of kinematics, including the use of equations of motion
  • Proficiency in unit conversion, especially between joules and electron volts
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  • Study the relationship between energy in electron volts and joules for particle physics
  • Learn about the principles of electric fields and their effects on charged particles
  • Explore advanced kinematic equations for varying acceleration scenarios
  • Investigate the implications of relativistic effects on electron velocities at high energies
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in the dynamics of charged particles in electric fields, particularly in the context of electron behavior and energy calculations.

brad sue
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Homework Statement



Calculate the velocity of an electron with 3 eV energy. This electron is accelerated by a constant field of 10 V/cm (parallel to the electron velocity) for 0.1 cm. What is the new electron velocity?

My other problem is the unit for the electric field . it bothers me: V/cm usually it is N/C

Homework Equations


.5*m*v^2

Please can i have some suggestions?

The Attempt at a Solution


3eV=3 x 1.6E-19=4.8E-19 joules=1/2 mv^2, so v^2=4.8E-19/4.5E-31=1E12
so v=10^6 metres/sec.
 
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You should be aware of the fact that 1 V/m = 1 N/C. So 1 V/cm is how many N/C?
 
100 N/C
thank i forgot all those units!

to find the final speed, i use the formula (Vfinal)^2-(Vinitial)^2=2a*(0.1 e-2)
when i did I found Vfinal =1.03 e6 m/s

the velocity difference i think is very small , it seems not right. did i do the question corretly?
thank you
 
Last edited:

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