Further Thoughts from C.D. Prewitt on Electricity Safety, A.C. vs. D.C.

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A direct current shock of this magnitude might kill you, but small ones aren't dangerous.

MOTHER EARTH NEWS contained some feedback on my statements about the advantages of direct over alternating
current, and I’d like to offer a rebuttal that’s based on
my own experience . . . not on theory, as the criticisms
seem to be.

First of all, an alleged danger of D.C. is that one might
not be able to let go of the electrodes that are producing
the shock. Now, I’ve been hearing that statement all my
life, and I’m convinced that it’s nothing but theory, with
no real foundation. I’ve had all sorts of shocks–up
to and including one of 10,000 volts, when one contact was
with my left had and the other with both feet thoroughly
grounded–and I’ve never felt any inclination to hold
on. On the contrary, either kind of current causes an
irresistible urge to disengage, which some people feel so
strongly that they claim the jolt has “knocked me down.”
I’ve seen victims do some wild jumping, but I’ve never seen
one want to continue grasping the conductor.

In fact, I wonder whether shocks are necessarily as deadly
as is generally believed. That time I was hit with 10,000
volts (A.C.) I didn’t dare pick up a cup of coffee for
three days afterward because I was sure I’d slosh it all
over the room. I was convinced that my nervous system had
had it . . . yet a week later I was as good as new. If some
people’s notions are true, my heart must have moved out of
the way.

Yes, I admit that even a small current could kill you if it
passed through the heart . . . but to accomplish that you’d
probably have to introduce electrodes into the organ.
Actually, of course, a current (unless it’s of very high
frequency) doesn’t flow through one geometric line, but
through a considerable area. In a case like my accident,
one’s heart might or might not get a lethal amount.

By the way, Peter Grant’s statement that the body’s
resistance is only 500 ohms is clearly out of line . . .
it’s known that across any substantial part of the
anatomy–as from hand to hand–the figure is well
up in the thousands of ohms. Since I had no exact data of
my own on this point, I made a test by thoroughly wetting
my hands and grasping the prods of an ohmmeter. I got a
reading of 50,000 ! I then attached the prods to
sizable pieces of metal (something no one would do where
there was shock hazard). When I again wet my hands and
gripped these conductors, I couldn’t get the indicator
below 20,000 ohms.

Now don’t misunderstand me! Current can be dangerous,
especially if you don’t know what you’re doing, and there
are some chances no one should take. (For example, don’t
risk shocks of any kind when you’re working in a
high place . . . on a windmill, perhaps. If you feel the
current it’s likely that you’ll instinctively jump away
from it, and you may lose your hold and fall.)
Nevertheless, there’s a theory–one I subscribe
to–that most so-called shock deaths are really caused
by fright. Certainly a severe jolt can be an alarming

But whether or not electricity is as harmful to the body as
most people think, I continue to believe that the danger is
less from D.C. than from A.C. . . . and with reason. By the
time I was ten years old we kids had our workshop (an
abandoned corn crib) stocked with enough No. 6 dry cells to
give us 110 volts D.C., which we played with all the time.
If we’d fooled around with that much A.C. I doubt that I’d
be writing now.

I’ve also done some experiments since then that bear out my
belief. For instance, at one time a neighboring town had a
community generating plant that put out 110 volts D.C. When
I was in that facility with some other workers installing
electrical equipment, I got to wondering what that amount
of direct current would feel like. Then an opportunity
presented itself and I grasped the blades of the main
switch. I’m sure that my hands couldn’t have been very
dry since we were working in a rather warm room–and I
didn’t put anything on them to increase resistance . . .
yet I could feel only the ripple of the current, which
wasn’t at all uncomfortable. I held on until my skin began
to get hot, at which point no effort was required to
release the control . . . I simply let go.

Here’s another case: In the early days of radio a good many
receivers–including all amateur models–were
D.C., and tubes required a plate voltage of 90 volts of
direct current. Since “B” batteries weren’t being made (or
at least weren’t available locally), some of us solved the
problem by building battery holders that would contain 60
flashlight “D” cells connected together in series. Because
this was little more than a “breadboard” arrangement, I’ve
felt 90 volts D.C. many times. There’s certainly no
tendency to hang on and the sensation isn’t very
disagreeable. But don’t try touching 90 volts A.C. or
you’ll learn something fast.

I have 400 volts D.C. available right here beside me, and
use it frequently. I have often come into contact with that
source, but I don’t take any special precautions because I
know it isn’t very dangerous . . . much less so than 110
volts A.C. I’ll stick to my guns and continue to recommend
direct current if you can possibly get it. It’s safer and
more satisfactory.

You see, I feel safe with my conclusions because they’re
based on experience. Theory can work well when it’s correct
and complete . . . but when it’s founded largely on hearsay
and not backed by practice, it can be dangerous.