Imagine waking up one fine morning, ready to take on the new day with excitement and
enthusiasm.
You get out of the bed and walk towards the bathroom, but the moment you touch the door
knob—ZAP!
You get a static electricity shock!
Thankfully, that type of shock is nothing but a minor inconvenience, but electric shocks
can be very dangerous, and even fatal, in some cases.
The question is—just how much electric current can the human body actually withstand?
The amount of current flowing through a circuit is measured in amperes or amps, whereas the
potential difference between two points is measured in volts.
There’s also the electrical circuit’s resistance to the flow of current, which is
measured in ohms.
To put this all in perspective, think of it like the flow of water through a pipe.
The water pressure is the voltage—which is expressed in volts—and the volume of
water is the amperage—which is measured in amperes or amps.
Resistance, which is measured in ohms, is a bit like friction that the insides of the
pipe offer to the flow of water.
There's a basic law in electricity, called Ohm’s law, which you will invariably come
across while studying anything related to electricity.
The law defines the relationship between voltage and current flowing through a circuit.
Mathematically, it states that voltage is equal to the product of current and resistance.
In other words, it means that the amount of current flowing through an electrical circuit
is proportional to its voltage.
To put it simply, it says that higher the number of amps, the greater the number of
volts.
You may have seen warning messages on electrical boards and generators imprinted with the universally
recognized emblem of danger: a human skull floating above two crossed bones.
In addition to this symbol, there’s also the rating of the machine in question, which
typically highlights the voltage range at which it operates.
These warnings tell us that direct, unprotected physical contact with the machine could be
fatal.
Because these boards and many other warning signs consist of voltage ratings, people tend
to get the idea that a certain threshold of volts can be lethal for humans.
Also, there’s a simple psychological consideration here; offhand, it would seem that 10,000 volts
would be deadlier than 100 volts, but this is SO not true!
People can get electrocuted by house appliances that operate at only 110 or 230 volts.
In fact, there have been cases of electrocution by electrical apparatus that use as little
as 42 volts of direct current.
This is why the real measure of a shock’s severity lies in the amount of current, or
the number of amps being forced through the body, not the voltage.
Although it’s true that more voltage draws more power, the thing that ACTUALLY kills
a person is the number of amps forced through their body.
Any amount of current over 10 milliamps is capable of producing severe shocks, but currents
in the range of 100 to 200 milliamps could be very painful and even fatal.
Currents above 200 milliamps may produce severe burns and unconsciousness, but if immediate
medical assistance is provided, the victim may still be saved.
If more than 200 milliamps pass through a person’s body, the muscular contractions
are so severe that the heart is forcibly clamped shut during the shock.
This is why providing immediate medical attention is the only way to improve the victim’s
chances of survival, as their heart may need to be restarted!
Now, this doesn't mean that it’s just the amps that kill you, and that voltage has no
role to play.
Without voltage or a potential difference, there would be no current AT ALL.
In order for current to flow, there must be a potential difference between two points.
That's why birds sitting on high power lines don't get electrocuted.
You may have heard the saying, “It's not the volts that kill you, it's the amps”
pertaining to electrical shocks.
Sure, it’s the current that’s responsible for causing harm, but current can only flow
and be dangerous when certain other things are also in place.
In reality, it’s a combination of the volts, amps, frequency and duration of current that
deals a lethal blow to the body.
If it were just the amps, then static electricity shocks, like those you occasionally get when
you touch doorknobs, would be lethal!
But they’re not.
Current can only be pushed through the body by volts, which can be lethal ONLY when they’re
pushed at a certain frequency for a long enough duration.
The condition of the skin plays a key role too, as a body’s resistance to the flow
of current may vary from 1000 ohms for wet skin to over 500,000 ohms for dry skin.
In other words, it means that the severity of an electrical shock would be HIGHER if
the skin is wet, because more current will flow due to low resistance.
Additionally, the actual resistance of the body also depends on the POINT OF CONTACT.
For instance, the internal resistance from hand to foot is nearly 500 Ohms, but only
100 Ohms between the ears.
So, more current could flow between the ears, which makes that area more prone to injuries
inflicted by current.
To put this all simply, the number of amps flowing through the body is JUST ONE aspect
of the nasty experience of getting an electrical shock; there are a bunch of other factors
that cannot be ignored.
Therefore, it’s best to avoid direct physical contact with anything actively conducting
electricity.
Electricity is a rather bizarre and potentially brutal beast.
When handled with care, it helps power the whole world, but even the slightest negligence
can lead to catastrophe!