Our nervous system is electrical in nature and is highly sensitive to external current. Electrical shock occours due to flow of current through the body when a voltage is imerssed on it.
(i) To prevent injury, the important quantity to control is current and not voltage. Comment.
(ii) What are the approximate values of electric current that :
(a) stop breaking.
(b) cause ventricular fibrillations and.
( c) cause series burns ?
(iii) A bird can roost on a high-voltage wire without being eletrocuted, How is a bird different from a man in this respect ?

Explanation

(i) Voltage is important only because it causes the charge to flow.
(ii) (a) Current less than `0.02 A` through the torso paralyeses the respiratory muscles and stops breathing.
(b) Current of about `0.1 A` through the region of heart will shock the heart muscles into rapid contractions (fibrillations)
( c) Currents of `1 A` or high through the body cause severe burns.
(iii) The bottom of the bird's foot is tough and not a good conductor of electricity. The only pd the bird experiences is due to the very small pd along the segment of the wire between the bird's feet.