Van de Graaff Human Chain

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★★ Only to be attempted with adequate safety procedures and trained staff

Categories: Van de Graaff Generator

Alternative titles: Passing the Charge

Summary

When people form a chain holding hands, with one person touching the dome of a Van de Graaff generator, the charge spreads through every person in the chain. If the last person in the line brings their free hand near a grounded object, all people in the chain receive a shock.

Procedure

Place the Van de Graaff generator in an open area with space for several volunteers.
Have one volunteer stand on an insulating platform and place their hand on the generator’s dome.
Ask several other volunteers to form a chain by holding hands with the first person, all being insulated from the floor (e.g. on tables or plastic mats).
Turn on the generator and allow charge to build up.
Have the last person in the chain carefully bring their free hand near a grounded rod or a metal object.
Observe the spark as the chain discharges.
After the demonstration, turn off the generator and discharge the dome with the grounding rod before anyone lets go.

Links

Physics -2018 - Van der Graaf chain - Clink's Class:

Physics 2021 - (2nd period) - The Big Shock - Clink's Class:

Variations

Try different numbers of people in the chain to see how far the charge can travel.
Perform in a darkened room to make sparks more visible.
Compare the effect with everyone standing on insulating mats versus standing on the floor.

Safety Precautions

Always discharge the dome with a grounding rod before anyone breaks the chain.
Ensure participants are not wearing or carrying sensitive electronics (phones, watches, hearing aids, pacemakers).
Warn participants that small shocks and sparks may be startling.
Use only healthy volunteers and avoid individuals with heart conditions or electronic medical implants.

Questions to Consider

How does the charge travel from the generator through the human chain?
Why does the spark appear at the last person when they approach a grounded object?
What role does the insulating platform play in this demonstration?
How is this related to how electricity flows in circuits?
What similarities exist between this demonstration and natural lightning discharges?