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AP® Physics 1 & 2

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Moderate

Pencil Lead Conductors

APPH12-YVRZKZ

A student connects one end of a battery to an ammeter and keeps the two remaining electrical leads open to perform tests of conductivity on various objects. The student tests two lengths of graphite by using unsharpened pencils with their erasures cut off. The first pencil is twice as long as the second pencil.

Which pencil will produce larger current in the ammeter and why?

A

The longer pencil will produce a larger current because the longer section of graphite has more resistance.

B

The longer pencil will produce a larger current because there are more atoms available in the resistor to create a current.

C

The shorter pencil will produce a larger current because resistance is proportional to length and current is inversely proportional to resistance.

D

The resistivity of graphite is constant for both pencils, therefore each pencil will produce the same current.