Lightining is a result of electrostatic discharge. Image credit zmescience.com

Lightining is a result of electrostatic discharge. Image credit zmescience.com

ZIMSEC O Level Combined Science Notes: Conductors and insulators

  • 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

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.


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