Lightning strikes can involve currents as high as 25,000 A...

Lightning strikes can involve currents as high as 25,000 A that last for about $40 \mu \mathrm{s}$. If a person is struck by a bolt of lightning with these properties, the current will pass through his body. We shall assume that his mass is $71.0 \mathrm{~kg},$ that he is wet (after all, he is in a rainstorm) and therefore has a resistance of $1.50 \mathrm{k} \Omega$, and that his body is all water (which is reasonable for a rough, but plausible, approximation). (a) By how many degrees Celsius would this lightning bolt increase the temperature of $71 \mathrm{~kg}$ of water? (b) Given that the internal body temperature is about $37^{\circ} \mathrm{C}$, would the person's temperature actually increase that much? Why not? What would happen first?

Key Concepts

Joule Heating

This concept involves the conversion of electrical energy into thermal energy when a current passes through a resistive material. The amount of energy converted (usually expressed in Joules) is directly proportional to the square of the current, the resistance of the material, and the time for which the current flows. It forms the basis for calculating how much heat is generated in any resistive medium due to an electric current.

Specific Heat Capacity

Specific heat capacity is a property of a substance that indicates how much energy is required to raise the temperature of a unit mass of the substance by one degree Celsius. In problems involving heating—such as calculating the temperature rise in a body assumed to be water—this concept links the amount of absorbed energy to the resulting change in temperature.

Localized Heating and Immediate Tissue Damage

While calculations based on Joule heating and specific heat might indicate a modest overall temperature increase, they do not account for the fact that energy deposition in biological tissue from a high-current event like a lightning strike is extremely non-uniform. Instead of uniformly raising the temperature, the sudden intense energy deposition can cause localized overheating, tissue burning, and other immediate destructive effects before any measurable overall temperature increase occurs.

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