Image Credits and References:
The generator was invented by Robert J. Van de Graaff and first demonstrated in 1931 http://www.browsebiography.com/bio-robert_van_de_graaff.html
This Rimstar video is long but a very accurate explanation of how Van de Graaff generators work https://www.youtube.com/watch?v=EsZQS2GOMQE
This video shows a fun and simple high-voltage experiment using a small generator https://www.youtube.com/watch?v=fTHOPe7mGIk&list=PL41778092B7768366&index=7
The task is to design, build and test a really big Van de Graaff generator. The voltage goal for the machine is 750,000 volts. Voltages approaching a million volts require the generator to have a tall column and a large metal sphere at the top. A fast charging time is achieved by a wide belt design that runs at high speed. The charge transport to the belt will be enhanced by a high-voltage power supply (+10 kV) at the generator’s base. Experiments and demonstrations will be conducted to show the effects of static electricity and to determine the machine’s operating voltage. Lastly, the generator will be combined with an evacuated column to make a particle accelerator. The effect of accelerated particles will be shown on a fluorescent screen and at a safe distance to avoid x-ray exposure.
Level of Difficulty: Medium
triboelectric series, corona discharge, electric field, ion, torque, DC motor, free and bound charges, Gauss’s Law, capacitance, electric triple point
“Triboelectric Effect” http://en.wikipedia.org/wiki/Triboelectric_effect
“Isolated Sphere Capacitor” http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capsph.html
Electrical Engineer (2) – The Electrical Engineers on the project are responsible for the variable DC motor drive that propels the belt at high speed. Additionally, the EEs will design and build the high-voltage supply that assists the deposition of charge on the belt. Other activities include the design and construction of a motor shaft speedometer to calculate the belt’s linear velocity.
Mechanical Engineer (2) – The Mechanical Engineers on the project are responsible for the machine’s overall structure, which includes the drive motor and transmission; a tall insulating column with the belt inside; and a large metallic sphere that receives the charge at a very high voltage. Additionally, the MEs will select the maximum belt speed by the transmission design and work to damp the belt against transverse and lateral oscillations. Special care will be taken to mount the sphere on the column in a way that is very secure and reduces the electric field enhancement at the triple point.
Physicist (2) – Physicists on the project are responsible for the design and construction of the various high-voltage experiments. In some cases, the experiments demonstrate to the public a basic principle of electrostatics, while other experiments are measurements of the generator’s fundamental properties; voltage, current, and charge.
Computer Scientist (2) – The Computer Scientists on the project are responsible for running electric field simulations of generator components to determine likely places for unwanted sparking. Other activities include a computer-based diagnostic system that records machine operating conditions vs. performance.
Designer (2) – Designers on the project blend the design goals of the various team members into a device that can be manufactured, maintained, assembled, transported, and is safe to operate in public demonstrations. Designers validate the system assembly with CAD illustrations and supervise all component manufacturing.
Journalist (1) – The Journalist documents the project’s progress on the website, communicates with the local media, and is responsible for a final report. The Journalist also works closely with the Multimedia Artist to provide video and graphic art displays for demonstrations that explain the project to the public. The whole project is your project.
Multimedia Artist (1) – The Artist also documents the project’s progress on the website and works with the Journalist to maintain the project’s presence on social media. Additionally, the Artist designs and organizes all public relations events to assure spectator safety and to enhance the community’s awareness of science and technology. The whole project is your project.
Business Manager (1) – The Business Manager is responsible for reporting the project’s progress against a predetermined schedule, determines critical path items to completion, and tracks project spending to assure that costs remain within a fixed budget. The Manager works with all team members to identify problems early and resolve them quickly. The whole project is your project.