PASCO EM-8812 Resistance Apparatus - Manual (Page 8)

®
R e s i s ta n c e A p p a r a t u s E x p e r i m e n t 1 : E x p l o r a t o r y S t u d y o f R e s i s t a n c e
8
Part B: Resistance Versus Diameter
Repeat step 1 above for the other diameters* of brass wires with = 24 cm.
Make a graph of R versus diameter (D). Is the relationship linear? Try an inverse
curve fit. Try and inverse-square curve fit. Which fits better? What does this tell you
about how R is related to D?
Part C: Resistivity of Brass
The resistance of any wire is given by:
(eq. 1-2)
where A is the cross-sectional area of the wire, and
ρ is the resistivity of the material.
Resistance depends on and A, but
ρ is a function of the material only.
Calculate A for each brass wire. Use Equation 1-2 and the values of R and from Part
B to calculate
ρ for each brass wire. Do you get about the same value for each? What
is the uncertainty of the calculated values? Compare your results to the accepted
value.
Part D: Resistivity of Other Metals
Test the copper, aluminum, nichrome, and stainless steel wires. For each wire, mea-
sure D, , V and I. Calculate R, A, and
ρ. Compare your values of resistivity to the
accepted values.
*If you have a
micrometer, measure the
diameters; otherwise,
use these values:
0.13 cm
0.10 cm
0.081 cm
0.051 cm
R
ρ
A
------ =