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.

a) Suppose a diode consists of a cylindrical cathode with a radius of 6.200×10^-2 cm , mounted coaxially within a cylindrical anode with a radius of 0.5580 cm . The potential difference between the anode and cathode is 240 V. An electron leaves the surface of the cathode with zero initial speed (). Find its speed when it strikes the anode.
Express your answer numerically in meters per second.




2- A 1.50 mm-diameter glass bead is positively charged. The potential difference between a point 1.50 mm from the bead and a point 3.60 mm from the bead is 460V . Note: The given distances are measured from the surface of the bead.
What is the charge on the bead?

Explanation / Answer

According to conservation of energy,
The energy gained by the electron in a potential is given by e * V.   This will be converted into its K.E when it reaches the anode. therefore e*V = (1/2)mv^2           v^2 = 2 * e * V / m
= 2 *( 1.602 * 10^-19) * 240 / (9.1 * 10^-31)                 = 84.50 * 10^(12)
V = 9.19*10^6 m/s .

* plz post single question

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