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How Much the maximum amount of voltage that our body can resist?

Posted in Electrical Engineering Common Knowledge by wahidyankf on November 1, 2008

Have you ever heard these sentences?

Be careful if u want to connect an electronic device…cause u can taste a

short circuit…

or

“hei…if u wanna repair your electrical installation, dont forget to use your

sandals…”

or maybe

“we will not be electrocuted when we use our sandals…”

In this post i will share my knowledge about these things. A knowledge that i got from my electromagnetic field’s class. The lecturer of this class is “eyang bambang anggoro”, one of the most inspiring lecturer in ITB’s School of Electrical Engineering and Informatics. I hope this post can be useful to us. And can make us more careful when we use electrical devices in our daily live.

Have a nice read!

Basically, all the things in earth can conduct electrical current. But, with different capability of course. There are things that can conduct electrical current with a good capabilities, those are things that we called conductor (most of them are metals, like bronze, gold, etc). There are things that have bad electrical current conduction, we called them isolator (Ex : woods, plastic, paper, etc). And also there are things that can conduct electrical current based on thermal condition around them, we call it semiconductor. At general, there are basic electrical properties. They are Resistance, Current, and Voltage. To understand these things, we can use street’s modelling. Here are these electrical properties modelling :

1. Resistance or we usually write R in electrical engineering.

If we compare it to the street, we can presuppose it as a level of road’s smoothness. It’s a logical thing that a car can drive flawlessly if the road is smooth, without any hole in the way. The bigger the resistance means bigger effort to cross the road, and vice versa.

2. Current or we usually write I in electrical engineering.

In this modelling, current is amount of car that may go accross the road per time scale. This amount of current has inverse relationship with road’s level of smoothness. What do you think if a car going through a road that is full of hole n rocks? It’s speed will become slower than when it’s travelling in smooth circuit. So, bigger Resistance means lower current accross the lane.

3. Potensial differences, or in electrical engineering we usually called voltage (V).

Let us imagine that the road is connecting Jakarta (name of the biggest city in Indonesia) and Bekasi (name of satellite city of jakarta, the citizens of Bekasi are usually working in offices located in Jakarta). When we use this modelling, voltage is the career oportunity in either city. Why people want to have a career in Jakarta? because the chance to become wealthy in Jakarta is bigger than in Bekasi. In order to do that, the people from Bekasi will make a journey to Jakarta to obtain their career. When will this humanoid current stop flowing? the answer is, when there are no potential differences between these cities. So do with potential differences, the electrical current will stop flowing when there are no potential differences between 2 point (eg. when the battery is leak).

In electrical engineering, point one, two, and three have a relation like this :

V = I x R

This equation means :

1. Bigger resistance means lower current going through the electrical circuit.

2. Bigger voltage means bigger electrical current through the electrical circuit.

Now, we go back to our heart. Our heart has natural resistance for about 5 kilo ohms (ohm is an electrical measurement unit for resistance). Our heart also have the maximum amount of current that can cross the lane for about 10 mili amperes (ampere is an electrical measurement unit for electrical current), where if we go accross the limit of this maximum value, our heart will have an abnormal function. And our heart will stop working when the electrical current accross our heart is about 15-20 mili amperes. Unfortunately, women have lower maximum electrical current that can cross their heart than men, they only need lower than 10 mili ampere to make their heart malfunctioned. We can compare this maximum electrical current with the road model. The traffic in the road will flow normally if the speed car accross the road is not too much, neither too slow. This is the reason why we often see maximum and minimum speed limit on the road. What do you think will happen if there are a cars that run too fast? There will be a crash on the road! so with our heart. We can’t let electrical current run too fast, neither too slow.

From this logic, now we go to scientifical equation for our heart. Above, we have equation :

V = I x R

If we calculate the variable of our heart, we can get the maximum voltage that our body can endure :

V = 10 mili Ampere x 5 Kilo Ohm

V = 50 Volts

And if we compare this value to our PLN’s (Indonesian State-owned Electrical Company) voltage in our home (220 volts), we will know that maximum voltage that we can endure (without using proper insulation, such as sandals, or shoes)is much lower than PLN’s voltage. Means that PLN’s voltage is able to kill us if we connect ourselves directly to the ground.

so, the lessons from this post are :

BE CAREFUL WHEN WE USE ELECTRICAL DEVICE OR ELECTRICAL NETWORK, BECAUSE THE PLN’S VOLTAGE ACROSS OUR HOME ARE ABLE TO KILL US.

USE ENOUGH INSULATION PROPERTIES IF WE WANT TO REPAIR AN ELECTRICAL DEVICE, SUCH AS SANDALS OR SHOES. IT WILL NOT GUARANTEE YOU 100% SAFETY, BUT IT WILL HELP YOU DECREASE YOUR CHANCE TO BECOME ELECTROCUTED.

Stand n Fight!!!

wahidyankf

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14 Responses

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  1. basementlabtek8 said, on November 1, 2008 at 6:05 pm

    nice post by wahidyan,thanks for your share.

    yes, we often neglect these kinds of common knowledge yet sometimes they can be very crucial (in fact, electrical students must always deal with risks of being electrocuted every time). Safety must always be put in first place.

    btw, those word(s) written in blue are edited due to verbal and/or grammatical errors.
    nice post though, keep contributing!

  2. wahidyankf said, on November 1, 2008 at 6:12 pm

    @ basement : thanks for your response and gramatical evaluation…hope i can do better english grammar for the next post… ^_^

    there you go, I put some corrections on your comment also :-P
    keep up your nice job, good luck!

  3. Fajar A. Prihandoyo said, on November 2, 2008 at 2:39 am

    basic knowledge !
    but very important !
    thx for your information

  4. wahidyankf said, on November 2, 2008 at 5:18 am

    @ basement : hahahaha…another gramatical errors… :lol:

    @ Fajar : thanks for your response…

  5. hamid said, on November 2, 2008 at 11:05 am

    that’s why
    when we go to the lab
    we must use our shoes

    once Edes (our lab legend) said to me
    “ru sure you want to wear those shoes, cos it’s very ugly and wet. u gone get your self killed if u wear those shoes in this lab (3 phase lab)”.

    thanks Edes

  6. andeh said, on November 2, 2008 at 1:09 pm

    mr. yoka,
    as far as i know, the basic electrical properties (or i may call it “electrical elements”) aren’t resistance, currents, and voltage.. they are current (I), voltage (V), charge (Q), and magnetic flux instead..

    1. the relationship between current and voltage produces resistance (measured in ohms),
    2. the relationship between voltage and charge produces capacitance (measured in farads),
    3. the relationship between current and magnetic flux produces inductance (measured in henries),
    4. the relationship between magnetic flux and charge produces memristor,

    (check this out : http://en.wikipedia.org/wiki/Electrical_element)

    CMIIW….

  7. wahidyankf said, on November 2, 2008 at 1:17 pm

    @ hamid : thanks for reading my article…yeah…safety is the first priority…i think that lab-das have the most reliable safety procedure than the other lab (that i ever learned my practicum class)…

    @ andeh : thanks for reading my article and your correction…i really appreciate that…i think i was wrong to intepret my mind…what i want to say here is there are 3 components that we usually learn at the first time for electrical circuit studies…like when we are still in High School and First Year time…thx btw… ^_^

  8. andeh said, on November 2, 2008 at 4:01 pm

    yups..
    those are “passive components”…

  9. robin septavyn said, on November 2, 2008 at 4:18 pm

    i had have experience about electrocuting.
    it was like my hand sucked in..whoooaaaa, what a wonderfull taste..
    how about you guys, have some story??…

    -it is my first comment in this blog..i hope we can gain something together-

  10. alfathakbar said, on November 4, 2008 at 1:25 pm

    maybe the next topic related to this one is “sandals/shoes can save you from electric shock”

    anybody? hehe

  11. EEng said, on November 6, 2008 at 2:14 pm

    if i am elle in heroes serial tv, i don’t care with electricity shock, because i am electricity shocker. haha…(junk mode on :D)

  12. wahidyankf said, on November 7, 2008 at 10:57 am

    @ robin : being electrocuted? its feel like my hand get shaked really hard…

    @ alfath : nice idea…anybody want to write that?hehe…

  13. Fanny said, on November 8, 2008 at 1:34 pm

    isn’t it 10mikroampere, the max current that can cross our heart? cross our body, 10miliamp max?
    huhu, just want to leave a comment.

    nice blog!

  14. asyarief said, on November 14, 2008 at 1:01 am

    have you ever been electrocuted?
    I have been electrocuted several times, even at the grid voltage (220V)…..

    And as you see…I can write this comment myself…I’m not dead (yet)…

    Well….What do you think about that?
    Is it because my body have a resistance value far above normal?
    Or is it because I just touch it for a while? Which means we have time properties at this case?


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