heat generated by an electric current in calories =
= 0.239 * (energy in joules) =
= 0.239 * (((current in amperes)^2) * (resistance in ohms) * (duration of exposure in seconds))
where:
• This is termed Joule's law.
• A calorie is the amount of heat required to raise the temperature of 1 gram of water 1 °C.
• 0.239 = 1 / 4.1868; 1 calorie (International Steam Table) = 4.1868 joules
Since current = (voltage) / (resistance)
heat generated in calories =
= 0.239 * (((voltage in volts)^2) / (resistance in ohms) * (duration of exposure in seconds))
approximate temperature increase in °C =
= (heat generated in calories) / (grams of body water)
where:
• This is an approximation since it assumes that all of the body weight is body water.
Interpretation:
• An brief increase in body temperature to 50°C is sufficient to cause irreversible heat denaturation of the central nervous system.
• Similar injury may occur at lower temperatures if the duration of exposure is sufficiently long.
