Lab Equipment for Teaching Physics

Features

• Measure work function of metal

• Study V-I characteristics of diode

• Demonstrate principle of magnetron tube

• Measure specific charge of electron (e/m)

  
  

Introduction

In metals, free electrons can move between atoms but are typically unable to escape the metal surface due to the attractive force exerted by positive nuclei, referred to as the surface barrier. However, if these free electrons gain sufficient energy, their kinetic energy increases, allowing them to overcome the surface barrier and escape from the metal.  

The minimum energy required for an electron to escape a metal surface is known as the work function or escape energy of the metal. Various energy sources can induce electron emission, including: Thermal energy (thermionic emission), Electrical energy (field emission), Optical energy (photoelectric emission) and Kinetic energy (secondary emission).  

This experimental apparatus focuses on studying the work function of metals using the principle of thermionic emission in a vacuum diode tube. In this method, the cathode metal is heated to a sufficiently high temperature, enabling free electrons to escape from its surface. The rate of electron emission increases with temperature.  

When an ideal vacuum diode tube is placed in a magnetic field perpendicular to the electron field, the emitted electrons experience a Lorentz force, causing them to follow a spiral trajectory. If the Lorentz force is strong enough, the electrons are prevented from reaching the anode, resulting in zero output current. This process demonstrates the principle of a magnetron tube. The charge-to-mass ratio (e/m), or specific charge of the electron, can then be calculated using the parameters of the magnetron tube.  

Using this apparatus, students can:  

1. Understand the concept of thermionic electron emission and verify the Schottky effect.  

2. Grasp the concept of the work function of a metal.  

3. Measure the work function of a metal using the Richardson straight-line method.  

4. Understand the principle of the magnetron and determine the charge-to-mass ratio (e/m) of electrons.  

The instruction manual provides detailed experimental configurations, theoretical principles, step-by-step guidance, and examples of experiment results. For additional information, please click  Experiment Theory and Contents to learn more about this apparatus. 

Specifications

Parts List