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Which of the following is used as a lubricant?

  • A.Graphite
  • B.Silica
  • C.Iron oxide
  • D.Diamond

Answer: A

Pencil 'lead' is graphite, mixed with clay and fired.

Graphite's carbon atoms lie in flat sheets held together only by weak forces, so the sheets slide off onto the paper as the pencil is drawn across it. More clay in the mixture gives a harder, fainter pencil.

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