Electrons in a television picture tube In a television picture tube electrons ar

Question

Electrons in a television picture tube
In a television picture tube electrons are boiled out of a very hot metal filament placed near a negative metal plate (see the figure). These electrons start out nearly at rest and are accelerated toward a positive metal plate. They pass through a hole in the positive plate on their way toward the picture screen. If the high-voltage supply in the television set maintains a potential difference of 15300 volts between the two plates, what speed do the electrons reach? (You can use the nonrelativistic approximation here.)

v =___________ m/s

Explanation / Answer

Given that Voltage V = 15300 V Initial velocity of electron is u =0 mass of electron m =9.11 x 10^-31 kg charge of the electron e = 1.6 x 10^-19 C ----------------------------------------------------- According to work energy theorem     Work done = Change in kinetic energy            eV = (1/2)mv^2 - (1/2)mu^2      So speed of the electron is                v = [(2eV)/m]                   = [(2( 1.6 x 10^-19 C)( 15300 V))/(9.11 x 10^-31 kg)]                   = 7.33 x10^+7 m/s

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