The voltage between the cathode and the screen of a television set is 22 kV.If we assume a speed of zero for an electron as it leaves the cathode,what is its speed just before it hits the screen? A)8.8 × 10⁷ m/s B)2.8 × 10⁶ m/s C)6.2 × 10⁷ m/s D)7.7 × 10¹⁵ m/s E)5.3 × 10⁷ m/s

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Quizplus · Accepted Answer

The correct answer is A because the kinetic energy of the electron is equal to the potential energy it gains in moving from the cathode to the screen. The potential energy is given by eV, where e is the charge of the electron and V is the voltage between the cathode and the screen. The kinetic energy is given by 1/2 mv^2, where m is the mass of the electron and v is its speed. Setting these two energies equal to each other, we get:eV = 1/2 mv^2v = sqrt(2eV/m)Plugging in the given values, we get:v = sqrt(2 * 1.602 * 10^-19 C * 22 kV / 9.109 * 10^-31 kg)v = 8.8 * 10^7 m/s

The Voltage Between the Cathode and the Screen of a Television