Schematic diagram of CRT

(Click figure to enlarge)

Schematic diagram of front panel

(Click diagram to enlarge)

Spiral trace of electron in magnetic field

## LEAI-47 Determining Specific Charge of Electron - Advanced Model

Features

• Complete apparatus

• Compact, stable, and affordable

• Demonstrates electron motion in electromagnetic field

• Measures e/m and geomagnetic component

Introduction

This LEAI-47 experiment apparatus is designed to determine the specific charge of an electron, or the electron charge/mass ratio (e/m), to demonstrate the motion properties of electron beam in electrical and magnetic fields, and to measure the geomagnetic component. It is an ideal teaching apparatus for physics laboratories in colleges and universities. This apparatus has the following advantages:

1. Three digital voltmeters for displaying various voltages independently.

2. All parts enclosed in a solid suitcase for convenient maintenance.

3. Three times of electron beam focusing, namely electron spiral motion ≥ 6π.

Using this apparatus, the following experiments can be performed:

1. Quantitatively measure the rules of electron movement in both electric and magnetic field.

a) Electrical deflection: electron + transversal electric field

b) Electrical focusing: electron + longitudinal electric field

c) Magnetic deflection: electron + transversal magnetic field

d) Spiral motion magnetic focusing: electron + longitudinal magnetic field

2. Determine e/m ratio of an electron and verify the polar coordinate equation of electron spiral motion.

3. Measure geomagnetic component.

Specifications

 Description Specifications Filament voltage 6.3 VAC; current 0.15 A High voltage UA2 600 ~ 1000 V Deflecting voltage -55 ~ 55 V Grid voltage UA1 0 ~ 240 V Control grid voltage UG 0 ~ 50 V magnetization current 0 - 2.4 A Solenoid parameters Longitudinal coil (long) length: 205 mm; inner dia: 90 mm; outer dia: 95 mm; number of turns: 1160 Transversal coil (small) length: 20 mm; inner dia: 60 mm; outer dia: 65 mm; number of turns: 380 Digital meters 3-1/2 digits Sensitivity of electrical deflection Y: ≥0.38 mm/V; X:  ≥0.25 mm/V Sensitivity of magnetic deflection Y: ≥0.08 mm/mA e/m measurement error ≤5.0%

Parts List

 Description Qty Main unit 1 CRT 1 Long coil (solenoid coil) 1 Small coil (deflection coil) 2 Division screen 1 Cable 2 Instructional manual 1

Schematic diagram of CRT

(Click figure to enlarge)

Schematic diagram of front panel

(Click diagram to enlarge)

Spiral trace of electron in magnetic field