Two insulating plates arc both uniformly charged in such a way that the potential difference between them is `V_(2) - V_(1)` = 20V (i.e. plate 2 is at a higher potential). The plate are separated by d = 0.1m and can be treated as infinitely large. An electron is released from rest on the inner surface of plate 1. What is its speed when it hits plate 2 ?
`(e = 1.6xx10^(-19) C m_(e)= 9.11xx10^(-31)` kg )

Options

A. `1.87xx10^(6) `m /s
B. `3.2xx10^(-18) `m/s
C. `2.65xx10^(6)` m/s
D. `7.02 xx10^(12)` m/s

Answer

A, B

Explanation

p.d. between plates= `V_(2) - V_(1) = 20`V The energy of electron in both the plates = `e (V_(2)-v_(1))`
If v is velocity of electron when it hits the other plate 2, then
`(1)/(2) mv^(2)= e(V_(2)-V_(1))`
`=sqrt((2e(V_(2)-V_(1)))/(m))`
`:. v= sqrt((2xx1.6xx10^(-19)xx20)/(9.11xx10^(-31)))`
`:. v = 2.65 xx10^(6) ms^(-1)`