ATM 10 Lecture Notes - Lecture 11: Short Circuit, Climatology, Ideal Gas Law
25 Sep 2016
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Lecture 11: november 12, 2014: lightning: what is lightning, lightning is an electrical discharge that extends typically 3-5 km and is ~1 inch in diameter. It is a very large spark traveling through a poor conductor (air: on average, about 100 lightning strikes occur each second on our planet. Each year, ~12,000 forest fires are ignited by lightning (compared to 62,000 due to human mishaps): currents generated in lightning are typically 15,000-30,000 amperes (a) which flash heats the adjacent air to. Lightning heats the air to ~30,000 c (~ 54,000 f): heated air expands (due to the ideal gas law) compressing adjacent air and a sound wave (thunder) is created. Sound travels about 340 m/s and light travels 3 x 108 m/s: you"ll usually see lightning first and then hear thunder. If you are too far away (~15km away), you may not hear the thunder even though you see the lightning: separating charge in a cloud.
