The following factors determine the severity of the effect electric shock has on your body:

The amount of body resistance you have to the

current flow.

The path the current takes through your body.

The length of time the current flows through your body.

Body Resistance

Resistance varies greatly in different parts of your body. A value of 1,500 ohms is commonly used as the resistance between major extremities of an average human body: hand to hand, or hand to foot.

For example, suppose you accidentally grabbed a wire carrying 120 volts alternating current (V ac). We can use Ohm's law, I = E/R, to figure how much current would flow through your body:

E = 120 V ac (the voltage you grabbed)

R =1,500 ohms (your average body resistance) Therefore:

I = 120/1,500 amp

I = .080 amp

I = 80 milliamperes

Therefore, if you grabbed a 120-V-ac wire, 80 milliamperes of current would flow through your body!

Table 3-1 shows the effects of varying amounts of electric shock on a normal person. In our example, you grabbed 80 milliamperes of current! That is 15 milliamperes beyond what could be fatal. It is also 70 milliamperes beyond the "can't-let-go" threshold for a 120-pound person and 62 milliamperes beyond what is needed to cause you to stop breathing.

Table 3-1.-Effects of Electric Shock

Remember, the 1,500 ohms is just an average value. Body resistance varies from person to person and may often be less than 1,500 ohms. When your skin is moist, your body resistance could be as low as 300 ohms! Also, breaks in your skin at the point of contact could reduce your skin resistance to nearly zero!

Skin resistance is only important when you are handling voltages of less than 240 volts. If you get shocked by more than 240 volts, the voltage arc will burn through your skin and leave deep, third-degree burns where it enters your body.

Current Flow Path

The two most dangerous paths that current can take through your body are (1) from hand to hand and (2) from left hand to either foot. The second path is the MOST dangerous since the current will flow through both your heart and other vital organs.

Current Flow Duration

Fibrillation is the shocking of your heart into a useless flutter. The longer you are shocked, the more chance there is for your heart to begin ffbrillatiog. Most people who die from electric shock die from fibrillation. Fibrillation in a normal adult is unlikely if the current in milliamperes is less than 116/t, where 'T' is the shock duration in seconds. The longer you are shocked, the less current is needed to cause heart fibrillation.

Some examples of shock current levels and durations that could cause fibrillation are:

21 milliamperes for 30 seconds,

44 milliamperes for 7 seconds, or

67 milliamperes for 3 seconds.