Physics - Senior Secondary 2 - Electric Field - Conduction of Electricity through Gases

Electric Field - Conduction of Electricity through Gases

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  4. Electric Field - Conduction of Electricity through Gases

TERM: 3RD TERM

WEEK: 2

Class: Senior Secondary School 2
Age: 16 years
Duration: 40 minutes for each of 5 periods
Date:
Subject: Physics
Topic: Electric Field – Conduction of Electricity through Gases
Subtopics:
• Hot cathode, thermionic emission
• The diode valve
• Application of hot cathode (thermionic) emission
i) Cathode-ray oscilloscope

SPECIFIC OBJECTIVES:
By the end of the lesson, students should be able to:

  1. Explain thermionic emission and its role in electricity conduction through gases.
  2. Describe the functioning of a diode valve.
  3. Identify applications of hot cathode emission, such as in a cathode-ray oscilloscope.

INSTRUCTIONAL TECHNIQUES:
• Explanation
• Demonstration
• Questions and answers
• Video clips on thermionic emission and cathode-ray oscilloscope

INSTRUCTIONAL MATERIALS:
• Hot cathode tube
• Diode valve
• Cathode-ray oscilloscope
• Physics textbook
• Whiteboard markers
• Videos on thermionic emission and cathode-ray oscilloscope

INSTRUCTIONAL PROCEDURES
PERIOD 1-5

PRESENTATION
STEP 1: INTRODUCTION
• The teacher introduces the concept of electricity conduction through gases.
• Students are asked if they have ever observed the glow in light bulbs and how electricity flows in a vacuum.

STEP 2: EXPLANATION
• The teacher explains thermionic emission: the release of electrons from a heated cathode.
• The teacher introduces the diode valve as a device that uses thermionic emission to allow current to flow in one direction.

STEP 3: DEMONSTRATION
• The teacher demonstrates the working of a diode valve.
• The teacher explains how thermionic emission is used in the cathode-ray oscilloscope to produce images on a screen.

STEP 4: APPLICATION OF HOT CATHODE EMISSION
• The teacher shows how cathode-ray oscilloscope works by displaying a video clip of a CRT in action.
• Students discuss the role of thermionic emission in the oscilloscope.

STEP 5: NOTE TAKING
• The teacher writes summary notes on the board for students to copy.
NOTE:

  • Thermionic Emission: The release of electrons from a heated cathode.
  • Diode Valve: A device that allows current to flow in only one direction, based on thermionic emission.
  • Cathode-Ray Oscilloscope: A device that uses thermionic emission to produce visual output for measuring electrical signals.

 

EVALUATION

  1. What is thermionic emission?
  2. Describe the function of a diode valve.
  3. How does the cathode-ray oscilloscope work?

 

CLASSWORK:
• Research another application of thermionic emission in everyday technology.

 

CONCLUSION
• The teacher will review the answers with the students and provide feedback.
• Students are encouraged to reflect on how thermionic emission is used in various devices.