High voltage or high current? where is the danger?
What is the main danger, the voltage or the current? Obviously if both are high the situation will be deadly, but which should be treated with more caution?
The answer is: current.
As discussed in another section , phenomena of static electricity may involve high voltages but with tiny currents. An example are the sparks observed when you remove a jumper (made of synthetic material) in the dark : this involves voltages of the order of 1000 V! But it is not harmful, because not enough electrons (low current) are participating. Danger is present only when there is a substantial amount of current .
Why is electricity dangerous to us?
Our organism is controlled by electric signals (although some regulation is performed by hormones-chemical signals). Our thoughts are a result of electric interactions in neurons. Our hearts are controlled by electric impulses... etc . That is why we are sensitive to electric signals that may interfere with or overpower the ones that regulate the functioning of our very complex bodies.
If a high electric current travels inside a human body, even burns may occur.
What levels of electric current are dangerous?
A current of 0.001 A can only be perceived, but a current of 0.005 A can produce pain. A current of 0.7 A, if sustained for at least 1s, and if it goes thorugh the heart, can cause death.
These are very common in third world countries and are notorious for causing accidents, sometimes fatal. A bad wiring or the absence of an earth wire can make a shower very dangerous.
In the case of showering, there is an extra hazard: the body is wet! Because tap water is a good conductor of electricity,the resistance of a wet body is greatly reduced and as a result any currents that may travel through the body will be much more itense and more likely to cause death.