The following is an email from a Malaysian received by Dr JB Lim

>To: All my dear friends be extra cautious when you need to help others, be very smart and alert at all times.
>
>It's a pity that things like this occur nowadays … you are warned to be cautious and do not take everything for granted.
>
>A NEW KIND OF RAPE (LADIES BE WARNED)
>
>This is a true story.
>
>The woman left the office after working hours and saw a little child crying on the road. Feeling pity for the child,


She went to ask what happened. The child said, 'I am lost. Can you take me home please?' Then the child gave her a slip of paper and tells the woman where the address is. The woman, being an average kind person who didn't suspect anything took the child there.

And then when they arrived at the child's 'home', the kind hearted woman pressed the door bell and she was electrocuted as the bell was wired with high voltage, and fainted..

>The next day when she woke up, she found herself in an empty house up in the hills, naked. Condoms were all thrown around with semen all over her and flowing from her body. There were at least about 20 condoms! She has not even seen her assailants. That's why nowadays crimes are targeted on kind people like her.

>Next time if the same situation occurs, never bring the child to the intended place.. If the child insists, then bring the child to the police station.

>Lost children are best sent and/or taken to police stations. Please send this to all your female friends/colleagues, and your male friends with girlfriends and wives. It is better to receive this email a thousand times than be a victim once!

>To keep my Identity and job safe I will just say that I am Officer Justice.

Keep safe Ladies!

>Please pass this on to family members. It is better to be informed. It is sad that we can't even help children now!
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Comment by Lim Ju Boo

How can it be possible for a person to be electrocuted and merely faint and able to wake up later? When a person is electrocuted, electricity passes through the body, and the heart is seriously affected. It goes into what we call ‘ventricular fibrillation’. This means the ventricles just quiver or shiver instead of contracting and pumping blood to the body.

Within minutes of electrocution the heart ceases to function, and without adequate blood flow to the brain the brain is dead within 3 minutes. The only way to revive the person is to instantly shock the heart back into normal rhythm using a defibrillator delivering several shocks between 150 -300 Joules of energy. There is an algorithm for this.

Applying CPR alone to restart the heart is normally not effective. In other words, when anyone is electrocuted, he simply dies. It is not a matter of just fainting and waking up later. I am not aware of any documented case where this is possible?

Who is this ‘Officer Justice’ the sender of this warning circular trying to bluff? She is sending pure rubbish to her friends and to other ignorant people. Ask her to speak to me. Just delete her ‘warning’ about her new form of rape.

lim ju boo

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Comments by Ir. KS Tan

Dear Dr Lim,

This is not logical. When a person presses an electrified door bell, the immediate reaction will be that the hand will fly off. Anyone who touches an electrified circuit will instantly fling off his hand. So the electric circuit is broken and no effect. Many people would have experienced this.
People die only when they are unable to get away from the electrified object. It is like holding the door of the fridge. You cannot remove your hand because the muscle seize by the electric current, involuntarily clamp on to the fridge handle. . Or the electric cable fall on your body and you go helpless into convulsion.

Rgds,
Khoon.

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Dear Ir. Khoon,

Thank you for your comment.

Unfortunately your half right, half wrong notion on electrocution has forced me here to lengthen my original short explanation.

You were right and also wrong at the same time. You have explained it half correctly. But because I wanted to make my explanation as short as possible without unnecessarily going into the complicated mechanism of reflex action, etc, I just gave the barest minimum about the effects of electricity on the heart. I am fully aware of what you said, but I did not want to make my comment too long with unnecessary physiology about reaction time, reflex action, etc.

Protective mechanisms operative:

Since you mentioned it, let me elaborate a little more on what you said. The body is always ready to protect itself from any danger, whether from electrocution, fire, falling body, infection, sudden threats of any kind…etc. Anybody who understands how the human body works, and the protective mechanisms always there in place, understands and appreciates this.

Overriding the body responses:

What is dangerous about touching and holding on to a electrified door handle, door bell, fridge handle (as illustrated by you) is that we always use the palm of the hand (palmar) to hold any object. Nobody ever grasp an object on the dorsum side (back of hand) because the fingers can flex from the dorsum position to the palmar position in order to grip on to the object on the palm. In short, we hold an object with the palm.

Anatomy of hand:

Unfortunately the joints, ligaments, tendons flexors and extensors of the extrinsic muscle of our finger are such that they restrict movements only in one direction – towards the palm. In other words the fingers anatomically cannot bend backwards away from an object. At best it can do is to open the fingers to their limits or flex the entire hand away from the object voluntarily by reflex action.

All or none law:

Unfortunately also, if an electric current is applied to any muscle it will contract automatically and this is not dependent on the strength of the current, except that the strength of the current need to reach a certain threshold to elicit a contraction. In physiology, we call this ‘all or none law’. I remember learning this in my physiology class as an undergraduate.

Muscles instantly contract:

Unfortunately also, if you hold on to a door handle, door bell, fridge handle, or any object which is electrified, it will instantly cause all the muscles of your fingers to contract towards the palm, causing you to hold on to the electrified object even tighter instead of relaxing your finger muscles outwards. This is an automatic instant response to an electric current.

Reflex Action:

But you were right if you only lightly touch the object with your finger tips. The reflex action will take a fraction of a second as the impulse will have to travel from the finger tips to the spinal cord where it will synapse across the cord, and travel back to the motor part of the fingers and muscles of the hands to ‘ask’ you to remove it.

But this takes some time because part of the message has to go to the brain also to let the brain interpret the stimulus on what to do. The brain has the discretion on what to do, although most of the reflex actions are involuntary to allow the body to react first, and the information can later be sent to the brain on ‘what happened’ and how did the body react to it. In order words, the reflexes takes over with the evasive action and the brain informed of the action taken later.

Speed of contraction faster than reflexes:

So far so good! But unfortunately the contraction of the muscles to an electrical current is so fast, much faster than impulses relayed to the spinal cord, and back again for the motor responses. Some of the impulses will ascend up the spinal cord to the brain of course for more decisive actions.

This is how the muscles react when stimulated by an electric current. Unfortunately it can only contract in one direction – towards the palm making the grip and the contact with the current even stronger.

Speed of nerve transmission:

When a stimulus is applied to the sensory receptor, the impulses travel to the efferent neuron to the interneuron junction in the spinal cord where the stimulus synapse across to the afferent neuron onwards to the muscles to contract (withdrawal reflex). The speed of this nerve transmission varies tremendously, and is between 0.9 - 89.41 m/s.

Speed of nerve reaction time vs. speed of electricity:

Even with the fastest transmission speed, it is still some 3 million times slower than the speed of electricity through a wire. It is slightly slower through a human body. The speed of electricity which is just a flow of electrons or ions through a conductor is some 96 % the speed of light through a copper wire. It may be about 240 000 km (240 000 000 meters) per second through a human body.

This means the body has no time to react at all because of the much, much slower reaction time. By the time even if the fingers or hand managed to withdraw by reflex reaction, the electricity would have already surged through the entire body at near (80 %) the speed of light. Instantly this would already affect the heart into ventricular fibrillation even if you managed to withdraw your hand.

Latent time:

Of course I do agree that there is a latent time. This means the muscle does not immediately respond to a stimulus, but that a period elapses between the stimulus and the commencement of the contraction, which is on the average is about the 100th of a second. This is termed the latent period. But since the stimulus (electricity) has already been applied, the muscles – skeletal as well as cardiac muscles will still respond accordingly - about 100thof a second later even if the hand has already withdrawn by reflex response. So there is no escape. The person will still suffer electrocution unfortunately.

Reaction time (RT):

This is time elapsed between the presentation of a sensory stimulus and the subsequent behavioral response. This time is between 150 - 200 milliseconds. On average, humans have a reaction time of 0.25 seconds to a visual stimulus, 0.17 for an audio stimulus, and 0.15 seconds for a touch stimulus. Reaction times vary from individual to individual. Because of the higher degree of neural processing, reaction times can be influenced by a variety of factors such as sleepiness, emotional distress, or consumption of alcohol. Still, no matter how fast the body reacts, it still is far, far, far slower than the speed of electricity through the body.

Electromyoneurophysiology:

I would not want to go too deep into electromyophysiology, signal strength, neurotransmission, neurochemistry of muscle contraction, (actin, myosin, ATP, etc), comparative speeds of nerve transmission, polarization and depolarization, migration of ions within the cells etc, etc. They would not only be too technical, but boring to others. Moreover, I am not a specialist in electro-neuro-myo-physiology to understand such intense technical complexity.

My simple original message:

My original comment is to make it as sweet, short and simple as possible for the lay readers about the effects of electrocution on cardiac rhythm (ventricular fibrillation) rather than trying to explain neurological effects and protective reflex responses.

My simple advice:

But if you suspect an object is electrified, always use a test pen, never touch it. But if you have none, but must test it with your hands, then always test it with the dorsum (back) of your hand. Using this technique, the fingers will contract towards the palm – away from the object. This way you will never be able to seize it even more firmly. Again, I have to repeat, the electricity would have already affected your heart if it is above the threshold to elicit the ‘all or none law’ (see above).

Death from electrocution is common:

Hence, death from electrocution is quite a common form of accidental death. Else, if your explanation is as simple as that, and completely right, then nobody can ever get electrocuted. They just remove their hands as you explained.

But it is not as simple as that when the speed of electricity is almost the speed of light. Your body’s reaction, speed of nerve transmission, and hence reflex action is tens million times slower than the speed of electricity.

Electricity is entirely different:

It is not like touching a hot iron where you only respond to a heat stimulus that hardly travels through the body. This is electricity that travels at near the speed of lights throughout the body, and your protective reflexes never be as fast as that.

You will still get electrocuted even if you managed to withdraw your hand. Your heart will already be in fibrillation. Someone needs to apply CPR instantly in the event of a cardiac arrest and shock your heart with a defibrillator once available as I have already explained in the last letter.

I hope my simple explanation here will help you to understand better, and also reach out to the lay people. Your comment has unnecessarily lengthened my original message.


Lim Ju Boo BSc PG Dip Nutr MSc MD PhD FRSPH FRSM

Special Medical and Science Adviser
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Dear Dr Lim,

Wow. Your writing is fantastic and awesome. May I borrow it for my PhD thesis?

However, not everything is correct. Not every time you touch an electric cable, you get electrocuted. Certainly not for the girl who rang the door bell with her index finger.
You need to understand electricity to understand why the girl is OK.

The electric equation V = IR means when the girl is wearing a high heel + rubber sole + a small push on the door bell button which is normally plastic, but now fixed up into metal by the bad guys, it means R is very, very big. So current is very small. The girl
just get a jolt. So nothing serious happened.

Rgds,
Khoon.

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Comment from Professor Dr Lee Chai Peng, Dept of Geology, University of Malaya

Have you not heard of taser or stunt-gun used by law enforcement officers in US and other places? Maybe the lady could not express herself so well but to a lay person that's how it appears when someone is hit by a stun-gun.

C.P.Lee

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Comment by Perry Tan

Wow! Thanks Dr. Lim for the lengthy and highly academic explanation of electrocution supported by the argument of the human anatomy of the hands and physiological thesis on the effects of strong electrical current through the human bodies that might and actually can cause tissue damage, cardiac arrest leading to ventricular fibrillation and in most cases, sudden death, which is obviously, irreversible.

It is such a professional presentation so well presented that, myself, as a common lay man, not only found it interesting but admittedly, it added on to my minisculte knowledge of both the human physiology and the incidence of electricity through the body.

Very Important Rule

Nevertheless, it reminded me of a VERY IMPORTANT RULE, OHM's Law. V = IR Where, V is inversely proportional to I if R is constant

Body and Skin Resistance

Can I confidently say that, the human body got its own Resistance, and there is such thing called Skin Resistance?

Applying Ohm's Law, the current drawn through the body depends on the resistance of the body. The resistance of human skin obviously varies from person to person and fluctuates at different times of the day, depending on the concentration of the bodily fluid and is probably proportional to the salt contents.

If the skin is dry, it is a poor conductor, and the resistance can be as high as R=100k Ω. If the skin is broken or wet, the resistance can be as low as 1 k Ω

(It is generally estimated that currents approaching 100 mA are lethal if they pass through sensitive portions of the body)

Assumptions and Calculations

Assuming that the door bell is connected to the domestic supply of 240 V AC, and the body resistance is 100k Ω, applying the V=IR,,, give us an I =0.0024 Amp which may cause electric shocks and convulsions but may not amount to a full electrocution.

Taking the average body resistance of 50k Ω, the current passing through the body works out to be I=0.0048 Amp which is still well below the threshold of 100mA =0.1 Amp.

Moreover, if the would be rape victim happens to wear platform shoes of 3 inches high heel, which is wood and with rubber soles, the chances of complete electrocution is further prevented. The shoes and rubber soles are poor conductors of electricity and the flow of electricity from the finger to the ground is incomplete.

Conclusion:

The chances of the rape victim to enter an electro-convulsion and survive the electric shock is high

As a layman, I believe, the would be rape victim wont die of electrocution.
The would be rapist wont want a dead body, and i guess they are knowledgeable enough to conduct a simple cpa, if not defibrillation, just to revive the victim to semi-conscious state.

Original Article and advice:

Prevention is better than cure, and the original advice to the ladies are of utmost importance.

Layman Disclaimer:

I may be wrong, and I sincerely hope my Ir friends from IEM can make some comments on electric calculation and prevention of electric shocks

Thanks Dr Lim

Perry Tan
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Dear Ir Rocky Wong,

You are the right person to comment on the Electric current issues.
Could you kindly give us your expert opinion please?

Warmest regards,
C K Cheong

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To All the Learned Gentlemen,

I am fascinated and at the same time amazed at the sudden landslide of volcanic eruption of information and knowledge derived from this forum that i may present this subject to my friends at a coffee talk discussion.

But one thing is sure; I would not want to be at the receiving end of an electrocution whether it is an accident or by intrusion through an assault.

Encore to all the parties who are giving so much enlightenment of the subject though.

Best wishes

An ordinary layman
David
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Hi Perry,

Your threshold figure of 100 mA is far too big. To feel an electric current, it must exceed 1 mA. To die by electrocution current through body must exceed 30 mA.
Your analysis of the girl surviving the door bell electrification is agreeable.
The girl may get an electric shock but will not die.

Rgds,
Khoon

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HI David,

Don’t try this at home.

But one thing is sure, I would not want to be at the receiving end of an electrocution whether it is an accident or by intrusion through an assault.

Yes. Nobody enjoys to be electrocuted. But there was a case in Brazil some time ago. The police came to investigate a death from electrocution. The man uses electricity to stimulate his sexual activity. Probably he steps down the electricity current for a tingling stimulating shock. But things went wrong and he got electrocuted instead. Cardiac arrest leading to ventricular fibrillation

Rgds,
Khoon.