What is Electric Shock Explain

The human failure in handling the electrical  components or  repairing the  distribution  system  without switching off the supply,an electric current touches or flows through the body, it is known as an electric

shock.The ultimate effect of electric shock on human body may be death.The result of electric shock on human body may be fatal  but it may be due to:

(a)  Fibrillation of heat i.e. damaging the heart to small pieces causing the stopping of breathing.

(b) Stopping of breathing action caused by blockade in the nervous system causing respiration.

(c)  Local over heating action or burning of the body due to sparking.

           The fibrillation of the hart is the most serious cause of death and there is no cure, although there 

is a possibility of rescuing a man who has suffered by the later two cause.

FACTORS ON WHICH INTENSITY OF ELECTRICAL SHOCK DEPEND

          (i)  The current strength : It has been experienced that in alternating current of low frequency,

the current  between 1 mA (miliampere) and 8 mA are just bearable, but current between 8 mA and 15

mA give a painful shock  which sometimes  contract  muscles too. If the leakage current is between 20 

mA and 50 mA and it passes through chest,it may stop breathing and current between 100 mA and 200

mA may cause fibrillation of heart. The current  beyond 200  mA will cause burn and it passes through heart even, it will not cause fibrillation of heart but may stop breathing  temporarily.Thus it is seen that 

it is the current which gives shock although  it depends upon  the  voltage. The leakage current is given as:

    The effect of current on the human body system is under:

          Miliamp.(mA)                                     Effect

    

    1 to 8 miliamp.                    Perceptible but not painful..

    8 to 15 miliamp.                  Painful shock,individual can let go at will,as muscular control is not lost

    15 to 20 miliamp.                Painful shock, muscular control of adjacent muscles lost, cannot go.

    20 to 50 miliamp.                Severe muscular contraction, breathing difficult.

    20 to 100 miliamp               Possible death, ventricular fibrillation, a heart condition that result in 

                                                instant death no known remedy.

    200 to above miliamp         Certain death, severe burns, muscular contraction extremely severe that

                                                chest musceles clamp down the heart and stop it during the duration of

                                                shock

                          I=E/R where E is the supply voltage and R is the body resistance.

          (ii)  The body resistance :-The body resistance is different under different condition, when the body is dry,  its resistance  varies  between  70000  ohm  and  1,00,000  ohm  per  square cm (the skin

resistance  is high while the  internal  resistance is low )   but when  the body is  wet, it is resistance is reduces to between 700  ohm  and  1000 ohm  per square  cm.  The average effective resistance  of the body may be taken as 50000 ohm when dry and 1000 ohm when wet.This high voltage causing current beyond 200 mA punctures  the  outer  skin  causing  burns.  The  table  below gives the results of shock under different conditions and under different voltage.

          Therefore, in wet situations, the body and contact resistance is low and therefore, even a small

leakage became dangerous.  Although  under  such conditions, 50 volts is  sufficient to prove fatal if applied for an appreciable time,this can only be considered as  exceptional.

        (iii)  Frequency of Current  :-   When the frequency is low, the electric shock is more severe 

and dangerous, and the direct current shock is most severe.

         (iv)  The path taken by the current through the body :- If the path of the leakage current is without

involving the chest of heart, survival is possible but there are severe  burns on the parts of the body involved in the shock depending u[on the value of current.

         (v)  Duration of the contact :-  If the duration of the contact is for a more time, the situation becomes dangerous due to numbness is the body  part  in  contact.  Such  electric  shock  becomes dangerous and sometimes fatal if contact is not broken within the earliest possible time.

         (vi)  Area of contact:-  Resistance decreases with the area of contact with the live part and the contact pressure. The accidents are nearly fatal in such situations.

ACTION TO BE  TAKEN IF A PERSON IS GETTING AN ELECTRIC SHOCK.

        (1)  If the main switch is close by, switch is off once. If not, ask someone to contact the substation 

supplying the area to cut off the  supply  temporarily.  Use the telephone or sent some one immediately.

Prevent any one else  rushing  ignorantly  out  to  rescue  the victim and getting himself electrocuted in trying to help, cordon off the area involved until supply is  cut  off.  Try to disconnect the persons from the  supply  by  any  means available if switching system is very near.  What is  required  is  immediate  action.

        (2)  If the voltage is 500 volts or below, every attempt should be made to free person from contact

 with the live wire after  protecting  oneself  with  any  dry  insulating  material. But in the case of high voltage circuit, switching off the supply obligatory.

        (3) To free the person from contact with the live wire,  stand on a  dray plank, stool, table or any other insulating object and pull the man away from the mains. If it is not possible, pull his coat if dry.

Use your own coat, dry cloth,paper,bamboo stick,wooden  pole  etc., either to pull or push the person without touching his body directly.Sometime the live wire itself (if LT)may be pulled or pushed away using dry bamboo  or any other dry stick such as walking stick.

        (4)  Send for a doctor..

        (5)  Observe the victim if he is unconscious and breathing normally. If  no, start giving artificial 

respiration without  any delay. It requires training  and  practice  to  give  artificial  respiration, in the  absence of which. it is more likely that the patient may be smothered. When the person regains consciousness, stimulants should be avoided unless ordered by the doctor.