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Solved: CP BIO Struck by Lightning. Lightning strikes can
Chapter 25, Problem 63P(choose chapter or problem)
Problem 63P
CP BIO Struck by Lightning. Lightning strikes can involve currents as high as 25,000 A that last for about 40 µs. 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 kΩ, 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°C, would the person’s temperature actually increase that much? Why not? What would happen first?
Questions & Answers
QUESTION:
Problem 63P
CP BIO Struck by Lightning. Lightning strikes can involve currents as high as 25,000 A that last for about 40 µs. 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 kΩ, 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°C, would the person’s temperature actually increase that much? Why not? What would happen first?
ANSWER:
Solution 63P
Step 1:
a) In this case we need to find out how much the temperature varies from the initial
temperature of the person.ie the change in temperature of the person.
The given values are
Current produced by the lightening, I =25000A
Mass of the person , m =75kg
The power distributed over the body by lightning, P = I2 R
P = (25000A)2 (1k)
P =6.25 10 11w