Question

The slope of plate characteristic of a vacuum tube diode for certain operating points ${10^{ - 3}}\dfrac{{mA}}{V}$​. The plate resistance of the diode and its nature respectively
(A) 100 kilo-ohms static
(B) 1000 kilo-ohms static
(C) 1000 kilo-ohms dynamic
(D) 100 kilo-ohms dynamic

Answer 1

Hint: The plate resistance is the inverse of the slope given. The conversion of ohms to kilo-ohms is necessary for finding the solution.

Complete Step by Step Solution: It has been given the slope of the plate characteristic of a vacuum tube diode for certain operating points ${10^{ - 3}}\dfrac{{mA}}{V}$​.
The plate resistance is given by the reciprocal of the slope of the vacuum tube diode. Thus, the plate resistance is, given by,
$R = \dfrac{1}{{slope}}$
$ \Rightarrow R = \dfrac{1}{{{{10}^{ - 3}} \times {{10}^{ - 3}}}} = {10^6}\Omega $
One kilo-ohms is equivalent to one thousand ohms.
Mathematically, $1k\Omega = 1000\Omega $.
The nature of the diode is static.

Hence, the correct answer is Option B,

Note: Vacuum tube diodes are also known as the Fleming valve, it could be used as a rectifier of alternating current and as a radio wave detector. This greatly improved the crystal set which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker, an adjustable point contact. Unlike modern semiconductors, such a diode required painstaking adjustment of the contact to the crystal in order for it to rectify. The tube was relatively immune to vibration, and thus vastly superior on shipboard duty, particularly for navy ships with the shock of weapon fire commonly knocking the sensitive but delicate galena off its sensitive point (the tube was in general no more sensitive as a radio detector, but was adjustment free). The diode tube was a reliable alternative for detecting radio signals. As electronic engineering advanced, notably during World War II, this function of a diode came to be considered as one type of demodulation. While firmly established by history, the term "detector" is not of itself descriptive and should be considered outdated. Higher-power diode tubes or power rectifiers found their way into power supply applications until they were eventually replaced first by selenium, and later, by silicon rectifiers in the 1960s.