In this topic we are learning to: z Examine how lightning occurs and how lightning conductors work. z Outline some uses of static electricity.
Lightning is one of the most visible and spectacular effects of static electricity.
The starting point for lightning is in cumulonimbus clouds, also known as ‘thunderheads’. These clouds carry a positive charge on top and a negative charge below. Friction between ice particles and water droplets within the clouds causes this charge.
Fig. 18.4.1 How lightning happens
Look at Fig. 18.4.1. The charge built up between the cloud and the ground causes a discharge of giant sparks, which is lightning.
Large electrostatic forces
Discharge (lightning)
1
There is a negative charge at the bottom of the cloud
2
Positive charge is generated
3 Lightning Conductors
Lightning will be more likely to strike taller or more pointed objects, such as trees. It happens especially if the object is a good conductor, such as a metal aerial.
To prevent these unwanted strikes, lightning conductors are used. They are often placed on the tallest building in a town. Lightning conductors are normally connected to a large metal plate below the ground.
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When the charge is large enough, the cloud discharges in a bolt of lightning
