Question

why diamond does not conduct electricity but graphite conduct electricity

Answer 1

This is because diamonds are insulator of electricity where as graphite is a conductor of electricity... So electricity passes easily through graphite & not diamond....

Answer 2

Correct answer by me :Graphite is an allotrope of carbon,carbon consists of 4 valence electron,each electron is connected to other three electrons in form of sheets ,forming the structure of carbon.However 1 electron is left behind ,it is free electron which conducts electricity.
In diamond each of the electron is connected to other 4 electron ,so no free electron is left behing and therefore diamond doesn't conduct electricity.