Dipil
Safety Consultant
Kesava Pillai
Occupational Safety & Health
Hansa Vyas
A Good Learner Always

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Dear Friends, A simple quiz on Electrical safety is attached. Try to answer and see where you stand, Regards, Kesava Pillai
From India, Kollam

Attached Files
 Quiz 6 Electrical.doc (145.5 KB, 5252 views)

Dear dipil,

I understand that there was some doubts about which is more dangerous to human body -AC or DC.

For ignorance we have no cure. Instead, if the engineers asked for some light we could have provided.

Electrical engineers are good at their own field - making electricity to work for them. Majority we came across had never even thought of the effect of electricity on human body. They know electricity causes shock and death. Their answers on other safety matters are often imaginary!

Now just ask them: What is ventricular fibrillation? What amount of current is required to cause ventricular fibrillation?

What is the minimum voltage at which one can feel electricity ?

What is the average resistance of human body?

What is the maximum resistance of human body?

Which part of the body has least resistance?

What is the minimum voltage required to pass sufficient current through the body to kill a person ? There are many more for a safety/Electrical engineer to understand in this field.

Coming to our issue : - Ask them what is the difference in rms value of AC and DC.

Kindly send these answers if you could get from the engineers who says DC is more dangeerous than AC on receipt of which I may be able to advise ASKCRITERION to provide the exact reasons why AC is more dangerous than DC.

Regards,

Kesava Pillai.

From India, Kollam
Dear sir,
let me try to answer the above question,
1.What is ventricular fibrillation? What amount of current is required to cause ventricular fibrillation?
A. Ventricular fibrillation, a serious heart condition may lead to death.It occurs at 50 to 100mA.
2.What is the minimum voltage at which one can feel electricity ?
1 to 8 mA -Perceptible, but not painful
3.What is the average resistance of human body?
Dry skin 1,00,000 to 6,00,000 ohms
Wet skin 1000 ohms
4.What is the maximum resistance of human body
5.Which part of the body has least resistance?
Ear to ear (about) 100 ohms
Regards,
hansa

From India, Udaipur
Dear Hansa.
1 is just an attempt but not clear for people to understand.
2 you expressed about current whereas the question is on voltage.
Let us wait and see for few days more to resolve the issue pl.
Regards,
Kesava Pillai

From India, Kollam
Dear Sir
Please go through the attached file. Four answers on the same from people in different field is attached.
Requesting you to give the exact answers to the mentione questions...
1. Why we are advising usage of 24V supply? Why we should believe 24V supply is safe?
2. How earthing can reduce the risk of receiving an electrical shock?
With regards,
Dipil Kumar V

From India

Attached Files
 Debate CiteHR - Answers.doc (35.0 KB, 1241 views)

Dear Friends,

I always insist “while a safetyman advises others on safety issues he is not to assume things and say I think……..” He has to give a definite answer -either yes or no. Often a safety issue becomes a matter of life and death as in the case of a confined space entry or a heavy lift. We can not take chances. We have to be certain in such issues. With regard to electricity also we have to be quite serious. If one is not sure he need not be ashamed to ask for experts/consultants.

As I mentioned electrical engineers are often not trained in safety. For sure they should be trained in safety and CPR. From the replies provided by them you can see where they stand and why they consider DC is more dangerous than AC. It is their opinion only. They are not sure.

The comparison on the effect of DC and AC is attached, (current in milliamperes)

1. AC is more dangerous than DC.

2. If our AC power supply is 220 Volts (RMS) then the actual peak voltage is about 310 V.

(To get same effect of say DC 220 volts we require peak voltage of 310 in AC and we call it AC 220 V.)

3. Interference with the normal rhythm of heart causes the condition called ventricular fibrillation. In this condition fibers of the heart muscles instead of contracting in coordinating manner (which causes heart to act as a pump) contract separately and at different times. When this happens, the heart's lower (pumping) chambers contract in a rapid, unsynchronized way. (The ventricles "flutter" rather than beat.) The heart pumps little or no blood. Blood circulation ceases and (unless proper resuscitation efforts made) death ensues. Heart cannot spontaneously recover from the condition. It is estimated that 50 ma is sufficient to cause Ventricular fibrillation.

4. 1.5 volts, a pen torch cell if touched with your tongue you feel the effect of current.

5. Average resistance of human body is considered as 1000 ohms. Internal resistance 400 – 600 ohms.

6. 6, 00,000 ohms. Skin on the palm of a village blacksmith who never used gloves in his life who can take a heated iron piece with his bare hands and sole of an old man who never used foot wear in his life. Callus – the dead cells or thickened skin on their hands and sole has that resistance.

7. Between the ears we have the least resistance of around 100 ohms only.

8. Minimum voltage required to pass sufficient current to kill a person is around 60 volts.

If the frequency is increased to thousands probably we may not even feel electricity. The normal supply frequency of 50 0r (60 as in USA) is all the more dangerous.

Regards,

Kesava Pillai

From India, Kollam

Attached Files
 EFFECT OF ELECTRICALCURRENT ON HUMAN BODY.doc (33.5 KB, 1101 views)

Dear Sir
Great reply!!! Thanks a lot for sharing!!!
I will share the info with all who participated in the discussions; with your kind permission!!!
Can you please elaborate the last sentence. Why it is so?
"If the frequency is increased to thousands probably we may not even feel electricity. The normal supply frequency of 50 0r (60 as in USA) is all the more dangerous."
With regards,
Dipil Kumar V

From India
@ Kesava Pillai
Dear Sir
Request you to bring such kind of interesting threads.
Lets us try to make this forum alive as like earlier.
With lots of hope I am writing this.
Thanks & Regards,
Dipil

From India
As per BOCW act & rule what is requirement of electrician work?
From India, Mumbai
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