Q. In a triode, cathode, grid and plate are at $0,\ - 2$ and $80\ V$ respectively. The electrons are emitted from the cathode with energy $3\ eV$. The energy of the electron reaching the plate is
A) 77 $eV$
B) 85 $eV$
C) 81 $eV$
D) 83 $eV$
Explanation
(d) There is a loss of kinetic energy of $2\ eV$ from filament to grid. The energy of the electron after passing through the grid will be $3 - 2 = 1\ eV$
The potential difference between plate and grid is $80 - ( - 2) = 82V$. The electron will gain energy $82\ eV$ from the grid to the plate. The energy of electron reaching the plate $= 1 + 82 = 83\ eV$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.