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$\mu$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 75 kg, that he is wet (after all, he is in a rainstorm) and therefore has a resistance of 1.0 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 75 kg of water? (b) Given that the internal body temperature is about 37$^\circ$C, would the person's temperature actually increase that much? Why not? What would happen first?

Key Concepts

Biological Effects of Electrical Shock

Beyond simple thermal effects, the passage of a high current through biological tissue can cause rapid and severe disruptions, including burns, tissue damage, and cellular disruption, long before any uniform increase in body temperature can be observed. The energy from such electrical events tends to cause localized damage and rapid phase changes, leading to injuries other than a mere temperature rise, highlighting the complex interplay between electrical energy and biological systems.

Electrical Resistance

Electrical resistance is a measure of the opposition to the flow of electric current through a material. It determines how much electrical energy is converted into thermal energy through Joule heating when current passes through a body or substance. Understanding resistance is crucial for predicting the heating effects in any system where current flows through a material.

Joule Heating

Joule heating refers to the process by which electrical energy is transformed into thermal energy when an electric current flows through a resistive material. This phenomenon, governed by the equation that relates power (or heat energy per unit time) to the square of the current multiplied by the resistance (P = I²R), is central to understanding how electrical energy is converted into heat in various systems.

Electric Power and Energy

Electric power and energy describe the rates and totals of energy conversion in electrical systems. Power, being the rate at which energy is transferred or converted (typically measured in watts), multiplies by time to give the total energy delivered. In scenarios involving short, high-current pulses, such as those in lightning strikes, even brief durations can deliver significant amounts of energy, which is then available to be converted into other forms such as heat.

Specific Heat Capacity

Specific heat capacity is the property of a material that defines the amount of heat energy required to raise the temperature of a unit mass of the material by one degree Celsius. In calculations involving temperature changes from delivered energy, the specific heat capacity provides the link between the thermal energy absorbed and the resulting temperature change, making it a fundamental concept in thermal physics and engineering.

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