The electron gun in an old TV picture tube accelerates electrons between two par

Question

The electron gun in an old TV picture tube accelerates electrons between two parallel plates 1.6 cm apart with a 30KV potential difference between them. The electrons enter through a small hole in the negative plate, accelerate, then exit through a small hole in the positive plate. Assume that the holes are small enough not to affect the electric field or potential What is the electric field strength between the plates? Express your answer to two significant figures and include the appropriate units. With what speed does an electron exit the electron gun it its entry speed is close to zero? Express your answer to two significant figures and include the appropriate units,

Explanation / Answer

here,

distance between the plates , d = 0.016 m

potential difference , V = 30 KV = 30000 V

a)

the electric feild strength between the plates , E = V/d

E = 3 * 10^4 /0.016 V/m

E = 1.88 * 10^6 V/m

b)

let the final speed of electron be v

work done by potential = kinetic energy gained

q * V = 0.5 * m * v^2

1.6 * 10^-19 * 3 * 10^4 = 0.5 * 9.1 * 10^-31 * v^2

solving for v

v = 1.03 * 10^8 m/s

the speed gained is 1.03 * 10^8 m/s

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