For dc and 50 Hz or 60 Hz ac currents, the human body can be approximated by a resistance. The current path typically considered is from one hand to both feet, or from one foot to the other one.

The internal resistance of the body is approximately 300 Ω, whereas values of body resistance including skin range from 500 Ω to 3000 Ω, as suggested in Daziel, Geddes and Baker , Gieiges, Kiselev [B94], and Osypka [B118].

The human body resistance is decreased by damage or puncture of the skin at the point of contact. Conducted extensive tests using saltwater to wet hands and feet to determine safe let-go currents, with hands and feet wet.

Values obtained using 60 Hz for men were as follows: the current was 9.0 mA; corresponding voltages were 21.0 V for hand-to-hand and 10.2 V for hand-to-feet.

Hence, the ac resistance for a hand-to-hand contact is equal to 21.0/0.009 or 2330 Ω, and the hand-to feet resistance equals 10.2/0.009 or 1130 Ω, based on this experiment.

Thus, for the purposes of this guide, the following resistances, in series with the body resistance, are assumed as follows:

a) Hand and foot contact resistances are equal to zero.
b) Glove and shoe resistances are equal to zero.

A value of 1000 Ω in Equation (10), which represents the resistance of a human body from hand-to-feet and also from hand-to-hand, or from one foot to the other foot, will be used throughout this guide. RB = 1000 Ω

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