The substance used in pencils is graphite, which also acts as a lubricant. It is used in pencils because its layered structure allows the layers to slide past each other easily, making it soft and slippery, enabling it to leave a mark on paper. This same slippery property makes it an excellent dry lubricant for various mechanical applications, especially at high temperatures where liquid lubricants would fail.
Which of following is used in pencils as a lubricant?
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