Millikan’s Apparatus, Electron Charge Demonstration Unit

Description

The Millikan’s Apparatus, also known as Millikan’s electron charge apparatus or an elementary charge measurement apparatus, is designed for investigating the fundamental electric charge using the controlled movement of charged particles between parallel metal plates. This laboratory instrument demonstrates the principles of Millikan’s oil drop experiment, adapted to use small latex spheres instead of oil droplets. By observing particle movement under gravitational and electrical forces, students can estimate the magnitude of the elementary electric charge. The apparatus uses an atomiser containing stabilised latex solution to produce fine particles. As these particles travel through a rubber hose, they acquire a static electric charge before entering the observation cell through a small needle.

Inside the observation cell, the charged latex particles move between two parallel metal plates separated by approximately 5 mm. An applied voltage creates an electric field that influences their movement according to their electric charge. The instrument features an adjustable cell voltage from approximately 0 to 300 V DC, allowing users to investigate particle behaviour at different electric field strengths. A polarity-reversing switch changes the direction of the field, allowing the movement of selected particles to be observed in both directions. A small telescope equipped with a graticule allows students to observe individual particles and measure their displacement against a graduated scale. The integrated illumination system helps make the small latex particles visible during experiments.

The Millikan’s Apparatus Without Power Supply requires separate external electrical sources. It provides connections for a 12 V AC/DC, 3 A illuminator supply and a suitable high-voltage DC power supply capable of providing approximately 300 V. The Millikan’s Apparatus With Power Supply includes the required electrical power sources within the instrument. This configuration allows the illumination and cell voltage systems to operate from the mains supply without separate external power units. Both configurations provide cell voltage adjustment, polarity reversal and measurement connections for a compatible student voltmeter or multimeter. These controls allow students to observe changes in particle velocity as the electric field is adjusted.

During an experiment, the movement of individual latex particles is measured over a known distance using the telescope graticule and a suitable timing device. By recording their rising and falling velocities at different applied voltages, students can analyse the forces acting on the particles. The collected measurements can be used to estimate the elementary electric charge, taking into account gravitational force, electrical force and viscous drag. The experiment also demonstrates that electric charge occurs in discrete multiples of a fundamental value.

These instruments are suitable for atomic physics, electrostatics, modern physics and advanced secondary or university laboratory experiments. They provide a practical method for studying charged particle motion and the relationship between electric fields and electrical forces. Safety Precautions: High-voltage electrical components must be operated according to the manufacturer’s instructions. Ensure electrical connections are secure before applying power, avoid contact with energised terminals and use the apparatus under appropriate supervision. Handle latex solutions carefully and clean the atomiser, rubber hose and needle after use to prevent blockages.

Each selected variation is supplied as one Millikan’s Apparatus in the chosen power supply configuration. The manufacturer documents an atomiser, latex solution, telescope, illumination assembly and observation cell as standard apparatus components. External power supplies are required separately for the model without an integrated supply, and a separate measurement meter may also be required.

LabChoice Australia supplies Millikan’s apparatus, atomic physics instruments and educational laboratory equipment for secondary schools, universities, physics departments, research institutions and science teaching facilities across Australia.