EFFECT OF CURRENT and ITS DURATION TO THE HUMAN BODY DURING ELECTRIC SHOCK

WHAT KILLS A PERSON? CURRENT OR VOLTAGE?

To answer the question, we need to put things in context. That means, there is no absolute. Current kills, but it needs to be present for a certain period of time.

The amount of energy delivered to the body is directly proportional to the length of time that the current flows; consequently, the degree of trauma is also directly proportional to the duration of the current. Three examples illustrate this concept:

1. Current flow through body tissues delivers energy in the form of heat. The magnitude of energy may be approximated by:

J = I²Rt

where J = energy, joules
I = current, amperes
R = resistance of the current path through the body, ohms
t = time of current flow, seconds

If sufficient heat is delivered, tissue burning and/or organ shutdown can occur. Note that the amount of heat that is delivered is directly proportional to the duration of the current (t).

2. Some portion of the externally caused current flow will tend to follow the current paths used by the body’s central nervous system. Since the external current is much larger than the normal current flow, damage can occur to the nervous system.

Note that nervous system damage can be fatal even with relatively short durations of current; however, increased duration heightens the chance that damage will occur.

3. Generally, a longer duration of current through the heart is more likely to cause ventricular fibrillation. Fibrillation seems to occur when the externally applied electric field overlaps with the body’s cardiac cycle. The likelihood of this event increases with time.

Also, we need to understand how much current is significant.

The magnitude of the current that flows through the body obeys Ohm’s law, that is,

I = E/R

where I = current magnitude, amperes (A)
E = applied voltage, volts (V)
R = resistance of path through which current flows, ohms (Ω)

Parts of the Body. 
Current flow affects the various bodily organs in different manners. For example, the heart can be caused to fibrillate with as little as 75 mA.

The diaphragm and the breathing system can be paralyzed, which possibly may be fatal without outside intervention, with less than 30 mA of current flow. The specific responses of the various body parts to current flow are covered in later sections.

Nominal Human Response to Current Magnitudes