Lightning – electrical energy from the sky

Rising streams of air generate electricity from mechanical energy by means of friction in the form of electrically charged clouds, up to a charge of 20 ampere-seconds (As). If the voltage difference between the storm cloud and the Earth is greater than 100 million V, a powerful discharge will occur as an electric arc. Because the discharge takes place within fractions of a second, high currents of up to 100,000 A can occur. For example, at a charge of 20 As and a discharge time of 0.4 ms, the current is 50,000 A. At this current, the power of a lightning bolt is 5 terawatts (TW). One TW equals one billion watts. Energy totaling 560 kWh is released in the process.

Information and ideas:
For further study, the physics of the gas discharge could be discussed. Another interesting exercise is to calculate the energy content of a bolt of lightning and to compare it with the calorific value of gasoline. What amount of gasoline corresponds to the energy of a bolt of lightning? Another example of the occurrence of electrical energy in nature is the electric eel, which produces electrical energy from a biochemical reaction.

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