Science:Lighting

• Clouds are poor conductors because they are made of mostly water particles
• They may become charged due to friction forces within them and with other clouds
• When these clouds discharge a flash of lightning can be observed
• This is similar to sparks that are seen when nylon clothes are removed in the dark
• Lightning is a much bigger spark but the principle is the same
• The excess electrons from the clouds flow towards the earth
• Lightning usually chooses the easiest path to the earth
• This usually means tall objects have a greater chance of being struck by lightning
• Lightning discharges can occur between:
• A cloud and the earth
• Two clouds with different charges
• Or between differently charged parts of the same cloud
• It’s cloud to ground discharges that pose the most danger to humans

Lightning conductors

Lightning conductor. Image credit physicsuneekacademy.blogspot.com

• Buildings can be protected from strikes using lightning conductors
• A good conducting material such as a copper wire, metal plate or pipe is put in the ground on one end
• The top end has spikes that are positively charged
• Because the negatively charged thunderclouds repel electrons from the spike end to the earth
• If the cloud discharges above or near the conductor the charge will most likely be attracted towards the spikes
• The conductor then carries the excess charge to the earth
• The lightning discharge is thus earthed

To access more topics go to the Combined Science Notes page.