Nuts and Volts - May/June 2018

Schematic Correx

In the February 2018 Q&A column, the incorrect schematic was used in Figure 4. Here is the correct diagram. We apologize for any inconvenience.

Don’t Get Zapped!

I really enjoyed Ward Silver’s recent column on high voltage and safety. However, there is a dangerously incorrect statement: "Better yet, the path from a hand to a foot doesn't go through the heart."

The hand to foot path most certainly DOES go through the heart — particularly when it’s from one hand to the opposite foot!!! See https://www.ncbi.nlm.nih.gov/ pmc/articles/PMC2763825/.

Furthermore, I have been taught and I believe that the hand to hand path — while certainly dangerous — is not necessarily the most dangerous. I have been taught (and it is intuitive) that the most dangerous path is from one hand to the other foot. This is born out from the following reference (Section 6. 5 seems to be publicly accessible). (Search was "electrical shock hand to hand vs. hand to foot.")

https://books.google.com/books?id=bd7hBQAAQBAJ&pg =PA102&lpg=PA102&dq=electrical+shock+hand+to+han d+vs+hand+to+foot&source=bl&ots=qZ4_JHkdMx&sig=u EtwyGAZNAj TpcXfqq8AzLGsDko&hl=en&sa=X&ved=0ah UKEwjl9t2g78vZAhUX4WMKHaghByIQ6AEIfjAI#v=onep age&q=electrical%20shock%20hand%20to%20hand% 20 vs%20hand%20to%20foot&f=false

So, while the classic "hand in the pocket" advice is certainly good, it is also critical that the feet and legs be insulated as well.

I strongly urge a correction be published of the erroneous statement that "Better yet, the path from a hand to a foot doesn't go through the heart" as it is dangerously incorrect.

Jay Jaeger

You're right, of course, that there is a path through the heart between the hand and foot. I probably should have written that as "doesn't go directly through the heart." I don't think there are any truly safe current paths through the body. I've put a note on the N&V website for the article and to remind folks to keep their feet insulated, too. Thanks for the feedback!