Download Converting the galvanometer into an ammeter: Rs

PHYCS 102 Lab.
Date:
Student Name:_____________________
ID No. :_______________
Student Partners:___________________
,_____________________
Sec. : (______)
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Experiment 5- The Galvanometer
1- Experiment Objectives
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2- Apparatus:
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3- Brief Theoretical Introduction:
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4- Data and Data Analysis:
4.1 The Galvanometer Sensitivity (d/IG ) and Resistance (RG):
 Use the indicated value for the maximum current (IGmax), i.e the current when the galvanometer
is at full scale.
 Use the indicated value for the galvanometer resistance RG.
 Record your values for IGmax and RG in the following table:
The Galvanometer Sensitivity and Resistance
RG ()
IGmax (mA)
Maximum No. of divisions (dmax)
dmax / IGmax (
)
4.2 Converting the galvanometer into ammeter
 Calculate the value of the shunt resistor (Rs ) that must be
RE
connected in parallel with the galvanometer in order to
convert it into an ammeter that can measure a maximum
current of Imax=1A.
Rs 
I G max RG

I max  I G max
A
RS
 .................()
G
 Calculate the required length (Ls) of a copper wire that has
a resistance Rs using :
Ls 
Rs A


 .................(m)
Where A=D2/4 is the wire’s cross sectional area and  is its resistivity.
 List your results in the following table:
Copper wire: Copper=1.72×10-8 (.m).
Rs ()
D  …… (mm)
A  ……… (m2)
Ls  ……. (m)
0.40
 Convert the galvanometer into an ammeter by connecting the shunt resistance Rs in parallel with the
galvanometer. For comparison, use this ammeter with another commercial ammeter to measure different
values of current and record your readings in the following table:
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Converting the galvanometer into an ammeter: Rs = …………….. ()
Division
d (div.)
Commercial Ammeter
reading IA (A)
Home made Ammeter reading
IHM = d×kA (A)
Percentage difference (%)
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6
9
12
15
 Plot a graph of IA vs. d and from the slope find the conversion factor kA.
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 Use the value of kA in order to convert the home ammeter readings from divisions to Amps. List your
calculations in the previous table.
 Compare the readings of the home made and commercial ammeters and find their percentage difference.
List your calculations in the previous table.
Conclusions:
What is the main thing that you have learned in this part of the experiment?
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4.2 Converting the galvanometer into a voltmeter
RE
 Calculate the value the resistor (RV) that must be connected in
series with the galvanometer in order to convert it into voltmeter that
can measure a maximum voltage of Vmax=5V.
V
RV  max  RG 
I G max
RV
G
 .................()
 Convert the galvanometer into a voltmeter by connecting the
resistance RV in series with the galvanometer. For comparison, use
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this voltmeter with another commercial voltmeter to measure various potential differences and record your
readings in the following table:
Converting the galvanometer into a voltmeter: RV =………………………()
Division
d (div.)
Commercial Voltmeter
reading VV (V)
Home made voltmeter reading
VHM = d×kV (V)
Percentage difference (%)
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6
9
12
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 Plot a graph of VV vs. d and from the slope find the conversion factor kV.
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 Use the value of kV in order to convert the home voltmeter readings from divisions to volts. List your
calculations in the previous table.
 Compare the readings of the home made and commercial voltmeters and find their percentage
difference. List your calculations in the previous table.
Conclusions:
What is the main thing that you have learned in this experiment?
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Questions:
Part I
-What is an ammeter?
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-Why it should be connected in series?
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-What should be the resistance of an ideal ammeter?
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- If you have asked to make an ammeter that measure a maximum current of 10 A, What changes you have
to make to achieve that?
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PartII
-What is a voltmeter?
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-Why it should be connected in parallel?
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-What should be the resistance of an ideal voltmeter?
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- If you have asked to make a voltmeter that measure a maximum voltage of 200V, What changes you
have to make to achieve that?
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