A bolt of lightning has enough energy to toast 100,000 slices of bread
It’s an awful lot of toast, but then a typical lightning bolt isn’t short on energy with over five billion Joules. This means that one typical strike could power a 1000 Watt, two slice toaster for 84,000 minutes in which time you could make around 100,000 slices of toast.
Static build up
Thunderstorms are an amazing natural spectacle, but even more amazing is the fact that we still don’t totally understand the processes which create lightning. What we do know is that lightning is a discharge of the static electricity that builds up in clouds in certain weather conditions. You’ve probably noticed that thunderstorms often happen on summer afternoons when the ground is warm and the air is humid. As the warm, humid air rises and meets cooler conditions higher up, water condenses out of the air to form clouds. The condensed water droplets then start to fall and collide with the warm air that is still rising.
All these little collisions give the water droplets a charge and for some, as yet unknown, reason the positively charged droplets find their way to the top of the cloud whilst the negatively charged droplets fall to the bottom. This separation of charge creates an electric field within the cloud which grows stronger as the charges build up and induces a positive charge in the ground directly below the cloud.
Air is normally a very good electrical insulator, but when the electric field becomes strong enough it ionises the air, separating it into negative and positive ions, and producing a conductive path between the cloud and ground. But the ionisation of the air isn’t uniform and zigzagged ‘step leaders’ start to appear from the cloud following the various conductive paths. At the same time positive streamers start reaching up from the ground, waiting for the step leaders to connect to them. Once a complete path is formed, there’s a deafening crack and the lightning reaches the ground.
With five billion Joules of electrical energy being discharged, the surrounding air becomes hotter than the surface of the Sun. We see this as a white flash and hear it as rumbles of thunder as the air rapidly expands.
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