1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Graphite, Pencil, and Paper

  1. Sep 30, 2004 #1
    How does the graphite in a pencil leave a mark on a sheet of paper? Any ideas? My answer is due tomorrow, so a clue or answer would be great.

  2. jcsd
  3. Sep 30, 2004 #2
    I would say that the friction is the main cause of the writing. When graphite is pushed down on paper, a force leaves marks on the paper, which would only happen with friction.
  4. Sep 30, 2004 #3
    It is because of the structure of graphite. As graphite is made of Carbon they must bond together. The Carbons form 3 bonds, but carbon should form 4 with each otehr, therefore there is a free electron to move and be put on the paper. Also, as graphite is layers of carbon, some layers come off as well.

    As a pencil is pulled along a piece of paper it leaves the graphite there.

    Hope that helps.

    The Bob (2004 ©)
  5. Sep 30, 2004 #4


    User Avatar
    Science Advisor
    Homework Helper

    Friction and shear cause cleaving between loosely bound sheets in the graphite lattice.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook