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Re: VanderGraaff safety (fwd)

. . . I ask a volunteer to place two
fingers of the same hand on the screw heads (to avoid sending any current
through the chest) . . .

Remember also that most commercial variacs are autotransformers and that one
side of the AC line is connected to earth ground. If the student is somehow
connected to ground, a low resistance path through the chest could result.

Depending on how the variac is wired, this could even present the full 120
volts between the student and ground - regardless of the variac dial
setting. (This of course can be checked and avoided.)

Perhaps an isolation transformer (or a 67.5 volt B battery) is advised.

Bob Sciamanda
Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor