The aim of this paper is to provide a way of teaching the factors that affect resistance using mechanical pencil leads and the brightness of the light given out by a light bulb connected to an electrical circuit. The resistance of a conductor is directly proportional to its length (L) and inversely proportional to its cross-sectional area (A). Additionally, the resistance depends on the type of conductor. Resistance R can be thus be expressed as R = ρL/A, where ρ is the resistivity of the conductor.
References
1.
L. D.
Wolf
and H. H.
Streckert
, “Graphite pencil line for exploring resistance
,” Phys. Teach.
34
, 440
–441
(Oct. 1996
). 2.
M.
Kamata
and M.
Abe
, “Hand-drawn resistors and a simple tester using a light-emitting diode
,” Phys. Educ.
47
(6
), 741
–746
(2012
). 3.
S.
Derman
and A.
Goykadosh
, “A pencil-and-tape electricity experiment
,” Phys. Teach.
37
, 400
–402
(Oct. 1999
). 4.
H.
Marshall
, “Pencil leads: 20 project ideas
,” Phys. Educ.
38
, 94
–96
(2003
). © 2015 American Association of Physics Teachers.
2015
American Association of Physics Teachers
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.