How does electric current cause death?

Electrocution depends on the amount of current that flows through or over the body. It may be determined by the formula I = E/R (Ohm's Law), where I is current and is expressed in amperes, E is voltage and is expressed in volts, and R is resistance and is expressed in ohms.  The flow of the current through the body is greater, if the voltage is high or if the resistance is low.

High voltages (higher tensions) may cause the person to be thrown, while lower tensions, around 240 volts, cause muscle contraction due to which the person holds on to the source of the current. This is also dangerous, because severity is directly proportional to the duration of current flow.

If the body is well insulated it does not conduct the current and no harm results. Dry skin offer high resistance but the resistance is diminished when the skin is moist or covered with sweat. Blood has a low resistance and as such within the body, electricity tends to be conducted along blood vessels.

The intense heat, which may results from flash over produces burns. High voltage burns may be very severe with charring of the body. If the area of contact is relatively large e.g. when a hot wire is grasped with a wet hand or when a person is electrocuted in a bathtub, death may occur without any visible skin burning.

Electrocution also depends on the path of the current in our body. Death is more likely to occur if the brain stem or heart is in the direct path of the current. Circuits from any of the limbs to the head involve the brain stem and upper cervical cord.Arm-to-arm circuit may also involve the upper cervical cord. In these cases, death probably occurs from paralysis of the medullary (respiratory) centers. Arm-to-arm or left arm to either leg circuits, involve the heart and death occurs either from ventricular fibrillation or cardiac arrest without fibrillation.

Source : The Hindu