PHYCS 102 Lab.
Date:
Student Name:_____________________
ID No. :_______________
Student Partners:___________________
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Sec. : (______)
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Experiment 4- Wheatstone Bridge
1- Experiment Objectives
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2- Apparatus:
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3- Brief Theoretical Introduction:
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4-1

Re
+ -
4- Data and Data Analysis:
4.1 (Part I): Measuring the resistance (Rx ) of
an unknown resistor: (Rx=RsL1/L2)
Rs
(Resistance Box)
Rx
 Follow the manual instructions to measure the
G
resistance of an unknown resistor Rx .
 Record the readings of both lengths L1 and L2 when
L2
L1
the bridge is balanced in the following table.
 (Note: Use proper values of Rs i.e. the balanced point must be within the range of L1+L2)
(Rx)th = …………….  …………… (
Rs ()
L1  ……. ( m )
)
L2  …….. ( m )
 Plot a proper graph and find Rx
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 Compare the measured value of Rx with the calculated one using the resistor’ color-coding and then find
the percentage difference in your result.
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4-2
4.2 (Part II): Measuring the resistivity () of a wire (R=L/A)
RE
 Follow the manual instructions to measure the resistance
of the conducting wire given to you.
 Replace the unknown resistor Rx by the wire and repeat
w
what you did in part (I) to measure the wire’s resistance.
Record the readings of both balance lengths L1 and L2 that
Rs
x
RX (Wire)
G
L1
L2
you obtain for the wire in the following table.
Resistivity of a conducting wire ()
Wire’s material: Constantan
Length L= 0.500  …… (m)
Rs ()
,Diameter D= 0.40  0.01 mm
L1  ……… (cm)
L2  …….. (cm)
 Plot a proper graph to determine value of Rx .
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 Use your result for the slope and calculate the wire’s resistivity () using R=L/A.
Where (A= π/4 D2 )
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 Find the percentage difference in the wire’s resistivity () by knowing that the Constantan
resistivity is (4.9 * 10-7 ) Ω.m
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5- Conclusions
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