by yamachem - uploaded on October 17, 2015, 2:34 am
This image was donated by Pearson Scott Foresman, an educational publisher, to Wikimedia Commons, and is thereby in the Public Domain.
you can see the source URL in the below comment.
This is a illustration of a lightning rod or lightning conductor which is an appliance to protect the structure in the event of lightning strike. If lightning hits the structure, it will preferentially strike the rod and be conducted to ground through the wire, instead of passing through the structure, where it could start a fire or cause electrocution.
For more info about lightning rod, see here:https://en.wikipedia.org/wiki/Lightning_rod