_:nfc7c648d4803444fa66d50700b102fa5xb21
<http://schema.org/reviewBody>
"If you hold one end of the tube and bring it near a Van de Graaff generator, the red, green, and blue lights come on in order as you walk closer to the generator (field gets stronger).  But don&#039;t touch the generator."
<https://www.teachersource.com/product/energy-tube/>