Lightning conductor consists of a long thick pointed copper rod with its lower end buried in the earth(earth plate) and the other end reaching above the highest part of the building and ending in several sharp spikes. -It is fixed to the side of the building.
The mode of action of lighting conductor.
When a negatively charged thunder-cloudpasses overhead it acts inductively on the conductor,charging the points positively and the earth plate negatively.
The negative charge on the plate is, of course, immediately dissipated into the surrounding earth. At the same time point action occurs at the spikes. Negative ions are attracted to the spikes and becomes discharged by giving up their electrons. These electrons then pass down the conductor and escape to earth.
At the same time positive ions are repelled upwards from the spikes and spread out to form what is called a space charge. This positive space charge, however, has a negligible effect in neutralizing the negative charge on the cloud.
Note:Without the protection of a lightning conductor the lightning usually strikes the highest point, generally a chimney, and the current passes to earth through the path of least resistance. Considerable heat is generated by the passage of the current and sometimes it may set into fire