What do thunderclouds and static charge have in common?
Inside a thundercloud, currents of air carry water droplets and ice particles upward. As the water droplets and ice particles travel inside the thundercloud, they rub against one another building up a static charge. The small, light positive particles rise to the top and the larger, heavier negative particles repel and move towards the bottom of the cloud.
Find out more about static charge and lightning in this fantastic learning module provided by NASA.