An Electric shock can occur upon contact of a human or animal body with any source of voltage high enough to cause sufficient current flow through the muscles or nerves. The minimum detectable current in humans is thought to be about 1 mA.  The current may cause tissue damage or heart fibrillation if it is sufficiently high.

Introduction :

• The level of voltage is not a direct guide to the level of injury or danger of death, despite the common misconception that it is.
• A small shock from static electricity may contain thousands of volts but has very little current behind it due to high internal resistance. 
• Physiological effects and damage are generally determined by current and duration. Even a low voltage causing a current of extended duration can be fatal. 
• It should be noted, however, that Ohm's Law directly correlates voltage and current for a given resistance; thus, for a particular path through the body under a particular set of conditions, a higher voltage will produce a higher current flow.

Causes of electric shock :

• Electric shock is caused by a difference in conduction of electricity across different surfaces. Electricity will always find the path to ground (or the completion of a circuit) that offers the least amount of resistance. 
• When any object providing less resistance than the normal circuit enters the path of the electrons, the current will leave the circuit and travel through the new path to ground. 
• This principle is why birds can stand on electrical wires and be safe, yet a downed electrical wire can be deadly for several hundred feet in all directions. 
• Electricity dissipates in various and unpredictable ways. 
• If you have a difference in voltage from one place to another, and there is a circuit completion (a wire, a finger) in between, current will jump across. 
• Electric shock is not the state of being electrically energized that can be totally harmless if controlled; it is the state of completing a circuit, or bridging the gap between conductors.