Van de Graaff Sparks

A Van de Graaff generator builds up static electric charge on its dome using a moving belt. When a grounded conducting rod is brought close, sparks jump between the rod and the dome. These sparks are similar to miniature lightning bolts and are accompanied by cracking sounds caused by rapidly expanding heated air.

1. Set up the Van de Graaff generator and grounding rod as shown in the demonstration setup.
2. Switch on the generator to begin building charge on the dome.
3. Slowly bring the grounded rod near the dome, keeping it slightly to one side for best results.
4. Observe sparks (mini lightning bolts) jumping between the dome and rod.
5. Move the rod around the dome to show sparks from different points.
6. When finished, turn off the generator and discharge any remaining charge by touching the dome with the grounding rod.

Van de Graaf Sparks - SMUPhysics:

📄 Van de Graaff Sparks - Classroom Physics Demos: https://demos.smu.ca/demos/e-n-m/50-van-de-graaf-sparks

• Use a larger dome or stack a smaller dome on top of a bigger Van de Graaff for larger sparks.
• Place an electroscope inside a plastic tube on the dome to visualize charge.
• Demonstrate hair-raising static effects by letting a student place their hand on the dome (with proper supervision and safety measures).
• Use fluorescent bulbs or other objects to show additional effects of static discharge.

• Always use the grounding rod to touch or discharge the dome—never touch with bare hands.
• Ensure good insulation between the machine and the ground for maximum effect.
• Perform only in dry air conditions to avoid weak discharges.
• Do not use near sensitive electronic devices.
• Warn participants that sparks may be startling and produce loud cracking sounds.

• How is the spark from a Van de Graaff generator similar to lightning?
• What causes the cracking sound when a spark occurs?
• Why does dry air make the sparks more visible?
• What role does the moving belt play in building up charge on the dome?
• How does this demonstration illustrate the concepts of induction, discharge, and static electricity?