1 Answers

The conductivity of gasses at low pressure can…

Posted by: 474 views , ,
PHYSICS

The conductivity of gasses at low pressure can be termed as

  • I. Hot cathode emission
  • II. Thermionic emission
  • III. Cold cathode emission
  • IV. Field emission
  • A. I & II
  • B. II & III
  • C. III & IV
  • D. IV & I

QUICK ANSWER…

C

DETAILS…

Let’s analyze each statement as follows:

  1. Hot cathode emission is the liberation of streams of electrons from a metal surface by subjecting it to intense heat. It is not the same as gas conductivity at low pressure.
  2. Thermionic emission basically means the same thing as hot cathode emission. Thermionic emission is the liberation of electrons from a metal surface by subjecting same to heat. This is different in concept from gas conductivity at low pressure.
  3. Cold cathode emission is the liberation of electrons when high voltage is applied to a low-pressure gas. Heat is not involved here.
  4. Field emission is the emission of electrons when a conductor is subjected to a strong electric field. This is basically what happens when gasses at low pressure is subjected to high potential difference.

I believe it is now obvious that III and IV are correct.

Now for the right answer to the above question:

  1. Option A is incorrect. in gas conduction at low pressure, electrons are liberated by high voltage and not by heat.
  2. Option B is incorrect.
  3. C is correct. during cold cathode emission, low pressure gasses are subjected to strong electric field.
  4. D is not the correct answer.

KEY-POINTS…

You may please note these/this:

  • Thermionic emission and hot-cathode emission simply mean the same thing, they are different names describing almost the same thing.
  • Field emission, cold-cathode emission, and low pressure gas conductivity all mean the same thing.

Use the questions and answer section to correct, express, and contribute your views.

You can also help share this page with friends.

/ culled from 2019 JAMB-UTME physics question 32 /

Answer Question