Van de Graaf generators and heart problems

Joel Gilmore said:

Hi all,

I run a group of physics performers that do physics shows
at primary and high schools. One demonstration that we do
is the Van de Graaf generator. This is a metal sphere that
is charged up to a high voltage, say 200,000V or more,
which is used to make sparks (say 5-20cm) and do other
electrostatic demonstrations. Currents are typically less
than 100 microamps (apparently!)

One demo is to get an audience member to place their hand
on the sphere, charging their body up, so that their hair
stands on end (each strand become like charged, and so
repels the other strands and the head itself.) However,
just recently, someone mentioned to me that they were no
longer allowed to do this in schools, because of the risk
of a heart attack to someone with a serious, undiagnosed
heart condition.

I can't find any real details about this on the web, so I
thought I'd ask some physicists and cardiologists for
their help. Is there any basis for this?

Not, ime.

Quoted message said:

Is the risk real?

It is probably more imagined than real.

Quoted message said:

Is simply being charged to high voltages dangerous, or is
it being discharged that causes the problem, i.e., when
you receive a spark, can the jolt from that cause
problems?

It is the joules of energy (volts times amps) that when
greater than 50 has the potential to cause cardiac arrest
rather than heart attack.

Quoted message said:

Anyone who could offer some literature supporting or
discrediting these ideas, or give some sound reasoning
would be greatly appreciated!

You are welcome, Joel.

Servant to the humblest person in the universe,

Andrew

--
Dr. Andrew B. Chung, MD/PhD
Board-Certified Cardiologist
heartmdphd.comheartmdphd.comOpen ↗

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Joel Gilmore said:

One demo is to get an audience member to place their hand
on the sphere, charging their body up, so that their hair
stands on end (each strand become like charged, and so
repels the other strands and the head itself.) However,
just recently, someone mentioned to me that they were no
longer allowed to do this in schools, because of the risk
of a heart attack to someone with a serious, undiagnosed
heart condition.

I can't find any real details about this on the web, so I
thought I'd ask some physicists and cardiologists for
their help. Is there any basis for this? Is the risk real?
Is simply being charged to high voltages dangerous, or is
it being discharged that causes the problem, i.e., when
you receive a spark, can the jolt from that cause
problems?

It is a real risk, now that it has been invented. No
responsible school board will want to run even
imaginary risks.

For comparison, you can look at electrified fences. These
typically give off several pulses a second, at order 10 kV,
with pulse energies between 100 mJ and 10 J/pulse. In most
countries use of these near public roads is allowed, under
suitable conditions. (certification, marking, etc)

The site you mention states that small Van de Graaff-s
will at worst be able to give off a 500 mJ pulse, so they
should be allowed in countries where electrified fencing
is allowed.

But that is by logic,

Jan

(J. J. Lodder) said:

Joel Gilmore <[email hidden]> wrote:

Quoted message said:

Quoted message said:

One demo is to get an audience member to place their hand
on the sphere, charging their body up, so that their hair
stands on end (each strand become like charged, and so
repels the other strands and the head itself.) However,
just recently, someone mentioned to me that they were no
longer allowed to do this in schools, because of the risk
of a heart attack to someone with a serious, undiagnosed
heart condition.

I can't find any real details about this on the web, so I
thought I'd ask some physicists and cardiologists for
their help. Is there any basis for this? Is the risk
real? Is simply being charged to high voltages dangerous,
or is it being discharged that causes the problem, i.e.,
when you receive a spark, can the jolt from that cause
problems?

Quoted message said:

It is a real risk, now that it has been invented. No
responsible school board will want to run even
imaginary risks.

Quoted message said:

For comparison, you can look at electrified fences. These
typically give off several pulses a second, at order 10 kV,
with pulse energies between 100 mJ and 10 J/pulse. In most
countries use of these near public roads is allowed, under
suitable conditions. (certification, marking, etc)

In the UK unmarked electrified fences are allowed beside
public roads when a hedge blocks public access to the wire.

I once watched a busload of drunk rock climbers stop to have
a [censored] on such a hedge. I suspect this possibility was not
considered by the legislators. The resultant scene was both
unforgettable and very difficult to describe.

--
Chris Malcolm [email hidden] +44 (0)131 651 3445 DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
["]http://www.dai.ed.ac.uk/homes/cam/]

Dr. Andrew B. Chung said:

Joel Gilmore wrote:

Quoted message said:

Quoted message said:

Quoted message said:

>>. snipped >>>>>>>>

It is the joules of energy (volts times amps) that when
greater than 50 has the potential to cause cardiac arrest
rather than heart attack.

Instantaneous Volt times instantaneous Amp is an
instantaneous Watt, not Joule. A Joule is a Watt-second.
A Joule being a measure of energy while a Watt is a
measure of power.

So, might 50 Joules, or 50 Watts have "the potential to
cause cardiac arrest rather than heart attack."

BTW, I saw this demonstration with a long haired girl (quite
memorable) some forty years ago. Surely, if there were a
problem, it would have emerged by now.

A.L.

Quoted message said:

<<<<<<<<<snipped >>>>>>>>>>

Joel Gilmore wrote

Quoted message said:

Is the risk real?

Yes. It is not the current (100 microamps are indeed
harmless). It is the charge. With the high voltage, you get
a peak current for a huge lot greater. If I go on a dry
flooring, and touch for example a door handle, I feel it as
very unpleasant.

Ulrich

J. J. Lodder said:

Joel Gilmore said:

One demo is to get an audience member to place their hand
on the sphere, charging their body up, so that their hair
stands on end (each strand become like charged, and so
repels the other strands and the head itself.) However,
just recently, someone mentioned to me that they were no
longer allowed to do this in schools, because of the risk
of a heart attack to someone with a serious, undiagnosed
heart condition.

I can't find any real details about this on the web, so I
thought I'd ask some physicists and cardiologists for
their help. Is there any basis for this? Is the risk real?
Is simply being charged to high voltages dangerous, or is
it being discharged that causes the problem, i.e., when
you receive a spark, can the jolt from that cause
problems?

It is a real risk, now that it has been invented. No
responsible school board will want to run even
imaginary risks.

Not sure if it's too off topic, but one could imagine a risk
with just about every science demo imaginable.

Anything with UV - burns, cataracts etc Potato/iodine test -
iodine is poisonous, allergy to potato mould Anything
flashing - epilepsy Magnets - explain why transcranial
magnetic stimulation could be dangerous

Care to add to the list of real, but probably miniscule
hazards that would frighten school boards?

--
Dirk

The Consensus:- The political party for the new millenium
theconsensus.orgtheconsensus.orgOpen ↗

Al. Lohse said:

Dr. Andrew B. Chung said:

Joel Gilmore wrote:

Quoted message said:

Quoted message said:

>>>. snipped >>>>>>>>

It is the joules of energy (volts times amps) that when
greater than 50 has the potential to cause cardiac
arrest rather than heart attack.

Instantaneous Volt times instantaneous Amp is an
instantaneous Watt, not Joule.

Correct. Joule of energy is proportional to volt times amps
times seconds. Thanks for correcting me.

Quoted message said:

A Joule is a Watt-second. A Joule being a measure of
energy while a Watt is a measure of power.

So, might 50 Joules, or 50 Watts have "the potential to
cause cardiac arrest rather than heart attack."

50 Joules when delivered at a time when the heart is
vulnerable does have the potential for causing ventricular
fibrillation (ie cardiac arrest).

Quoted message said:

BTW, I saw this demonstration with a long haired girl
(quite memorable) some forty years ago. Surely, if there
were a problem, it would have emerged by now.

Agree.

Servant to the humblest person in the universe,

Andrew

--
Dr. Andrew B. Chung, MD/PhD
Board-Certified Cardiologist
heartmdphd.comheartmdphd.comOpen ↗

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Joel Gilmore said:

Anyone who could offer some literature supporting or
discrediting these ideas, or give some sound reasoning
would be greatly appreciated! For information see
amasci.comsafe.htmlOpen ↗, with the latter
mentioning the danger.

That site is OK. The total energy is CV^2/2. It is correct
in warning against Leyden jars - do not increase the
capacitance.

But I do not understand the warning against human chains. I
believe that this is safer, because the energy is dissipated
by more people.

--
"Electrons damage the brain," said Farish. (Donna Tartt)

Chris Malcolm said:

[email hidden] (J. J. Lodder) writes:

Quoted message said:

Quoted message said:

It is a real risk, now that it has been invented. No
responsible school board will want to run even
imaginary risks.

Quoted message said:

For comparison, you can look at electrified fences. These
typically give off several pulses a second, at order 10
kV, with pulse energies between 100 mJ and 10 J/pulse. In
most countries use of these near public roads is allowed,
under suitable conditions. (certification, marking, etc)

In the UK unmarked electrified fences are allowed
beside public roads when a hedge blocks public access
to the wire.

I once watched a busload of drunk rock climbers stop to
have a [censored] on such a hedge. I suspect this possibility
was not considered by the legislators. The resultant scene
was both unforgettable and very difficult to describe.

Now that we are into applied home physics: it is a childrens
game to test live electrified fence with a blade of grass
and to dare each other about how short you can take it.

But a Van de Graaff for further education is out of course:
far too dangerous to expose the kiddies to,

Jan

PS This must be one of the most misspelled names in
physics, scoring far beyond Einstien and Hawkins. The
misspelled name was popularized by the rock band 'Van de
Graaf Generator'. The one and only correct spelling is
'Van de Graaff', without an r after 'de' and with a
double ff at the end.

Biographical detail, photos and explanations may found at
<http://chem.ch.huji.ac.il/~eugeniik/history/graaff.html>
with further references to other web resources.

"Al. Lohse" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Dr. Andrew B. Chung said:

Joel Gilmore said:

>>>>>>>>snipped >>>>>>>>>

Quoted message said:

It is the joules of energy (volts times amps) that when
greater than 50 has the potential to cause cardiac
arrest rather than heart attack.

Instantaneous Volt times instantaneous Amp is an
instantaneous Watt, not Joule. A Joule is a Watt-second. A
Joule being a measure of energy while a Watt is a measure
of power.

So, might 50 Joules, or 50 Watts have "the potential to
cause cardiac arrest rather than heart attack."

BTW, I saw this demonstration with a long haired girl
(quite memorable) some forty years ago. Surely, if there
were a problem, it would have emerged by now.

A.L.

Quoted message said:

Quoted message said:

p>>>>>>> snipped >>>>>>>>>

I have also seen them around for quite some time and used to
play with them in science labs. I have also seen them in
carnival side shows where a girl lights bulbs, shocks people
with quarters, etc. So I guess they are OK in normal
situations. If you have a heart condition, pacemaker, etc. I
don't know.

I think I would forgo the fun of having my hair stand
on end. 🙂

Bill

Dr. Andrew B. Chung said:

Joel Gilmore said:

Quoted message said:

>>>>>>>snipped >>>>>>>>>

Quoted message said:

It is the joules of energy (volts times amps) that when
greater than 50 has the potential to cause cardiac arrest
rather than heart attack.

Instantaneous Volt times instantaneous Amp is an
instantaneous Watt, not Joule. A Joule is a Watt-second.
A Joule being a measure of energy while a Watt is a
measure of power.

So, might 50 Joules, or 50 Watts have "the potential to
cause cardiac arrest rather than heart attack."

BTW, I saw this demonstration with a long haired girl (quite
memorable) some forty years ago. Surely, if there were a
problem, it would have emerged by now.

A.L.

Quoted message said:

Quoted message said:

p>>>>>>> snipped >>>>>>>