Electricity & Magnetism: Van de Graaff Generator

PIRA Class: 5A50.30

Purpose:
Produce large voltage by separating large amounts of electric charge.  

Description:
Show the electric discharge from Van de Graaff generator to a nearby grounded rod. See the other demo pages labeled (Van de Graaff) for demonstrations that use the Van de Graaff generator.

Beforehand:

- If during trial run no discharge is produced (and all connections, etc. are in order), securely attach a grounding lead from dome to base (with duct tape) and run belt motor for ~30 minutes. No HV (High Voltage)! This will help remove excess humidity from inside dome.

1. Locate Van de Graaff in classroom 5 feet away from any student/ student desk/ classroom electronics/ etc.

2. While standing on insulating stool and holding grounding rod in one hand, flip on belt motor with the other hand. (Continue standing on insulating stool while using generator.)

3. Gradually increase belt speed using knob on Van de Graaff generator.

4. When finished, reduce belt speed then turn off Van de Graaff generator. Once belt is no longer moving, touch grounding rod to dome one last time to insure that dome is completely discharged.

NOTE:

- Depending on the day's humidity, discharge will be small or large.

- Internal belt and brushes remove electrons from Van de Graaff dome, leaving dome positively charged. When brought in close contact, grounding rod replaces these negative charges; belt immediately strips them off again.

- Dome's potential will reach ~20,000V with respect to grounding rod.

- Here is a nice short video about demos and safety.

Equipment:
Van de Graaff generator, grounding rod, insulating stool

Location:
Shelf 352, insulating stool is in the back corner next to Shelf 164