Pencil lead composition
Early pencils contained lead, but the main components of the pencil refills used by people were graphite and binder, which no longer contained lead and were harmless to the human body.
Since the main component of a pencil is graphite, and graphite is a conductor, the lead of the pencil can conduct electricity. However, the electrical conductivity of the pencil lead is not very strong. Because of the arrangement of the atomic structure of graphite, it is determined that it can only conduct electricity in two dimensions, that is, it is conductive between two points on the same plane, while the upper and lower sides of the plane are not conductive. The graphite in the pencil lead is crushed and mixed with clay, so the atomic structure is disrupted, so the electrical conductivity is not very outstanding. In the experiment, if the length of the 2B pencil lead exceeds 15CM, the small bulb will not emit light. (Voltage is about 5V)