Mass of Electron Apparatus, Electromagnetic Field, 82 L x 115 W x 105mm H

This Mass of Electron Apparatus is a teaching instrument for demonstrating electron-beam deflection in a magnetic field and for estimating the electron mass using classical dynamics.

It employs a 'magic eye' style electron tube with a fluorescent screen to make the beam path visible.

Operating Principle

An electron beam travels from a central cathode to a surrounding anode, creating a visible fan-shaped glow on the fluorescent surface. When an external magnetic field is applied using an air-cored solenoid positioned around the tube, the beam curves due to the Lorentz force. Measuring this curvature under known electrical conditions enables calculation of the electron mass.

Summary of Experimental Setup

A low-voltage supply powers the tube heater, and a stable high-voltage DC source drives the anode. An air-cored solenoid is placed concentrically over the tube so that the beam passes near the solenoid midpoint.

A separate adjustable DC current source provides the solenoid field. The physical geometry ensures the beam is viewed at the field centre for consistent measurements.

Power & Accessories

Separate supplies are used for the heater (approximately 12 V AC/DC), the anode (smooth high-voltage DC), and the solenoid (smooth adjustable DC or constant-current).

A combined multi-output supply is available to simplify setup. Stable readings require maintaining constant coil current as the solenoid warms.

Construction & Design

This apparatus integrates the electron tube on a durable base with secure terminals and lead connections. It supports clear viewing down the solenoid bore for accurate observation of beam curvature. Designed and manufactured in Australia.

Product Features

• Visible Electron Beam: Fluorescent screen visualises beam path, improving engagement and conceptual understanding.
• Air-Cored Solenoid: Provides a well-defined magnetic field at the tube midpoint, enhancing measurement reliability.
• Independent Supplies: Separates heater, anode, and coil power to stabilise operating conditions and data quality.
• Repeatable Geometry: Fixed alignment of tube and coil supports consistent curvature measurements across trials.
• Quantitative Learning: Links observed curvature with field strength and accelerating voltage to reinforce core dynamics.
• Instructional Efficiency: Generalised setup and procedure streamline practical sessions, saving teaching time.
• Robust Build: Durable base and secure connections support routine classroom and laboratory use.
• Australian Manufactured: Locally engineered construction ensures quality and serviceability for education settings.