Before the advent of solid-state electronics, vacuum tubes were widely used in r

Question

Before the advent of solid-state electronics, vacuum tubes were widely used in radios and other devices. A simple type of vacuum tube known as a diode consists essentially of two electrodes within a highly evacuated enclosure. One electrode, the cathode, is maintained at a high temperature and emits electrons from its surface. A potential difference of a few hundred volts is maintained between the cathode and the other electrode, known as the anode, with the anode at the higher potential.

Suppose a diode consists of a cylindrical cathode with a radius of 6.200×102 cm , mounted coaxially within a cylindrical anode with a radius of 0.5580 cm . The potential difference between the anode and cathode is 265 V . An electron leaves the surface of the cathode with zero initial speed (vinitial=0). Find its speed vfinal when it strikes the anode.

Express your answer numerically in meters per second.

Explanation / Answer

Kinetic Energy gained by an Electron, = q*v
1/2 * MV^2 = Q*V
1/2 * 9.1 * 10^-31 * V^2 = 1.6 * 10^-19 * 265
V = 9.65 * 10^6 m/s

Speed of electron when it srtrikes the anode, v = 9.65 * 10^6 m/s

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