Multirange Ammeter magnitudes homework

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SUMMARY

The discussion focuses on calculating the required resistances R1, R2, and R3 to convert a galvanometer into a multirange ammeter capable of measuring currents of 10.0 A, 1.00 A, and 0.100 A. The galvanometer has a resistance of 48.0 ohms and deflects full scale at a current of 0.0200 A. The formula used for calculating the shunt resistor is Rsh = (Ifs * Rc) / (Ia - Ifs), where Ifs is the full-scale current, Rc is the galvanometer resistance, and Ia is the current being measured. It is confirmed that R1 is the shunt resistance while R2 and R3 are additional resistances in series with the meter.

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  • Knowledge of electrical resistance and Ohm's Law
  • Familiarity with shunt resistor calculations
  • Basic circuit analysis skills
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parm09
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Can someone please help me out with this problem? I am not sure if what I am doing

The question:

The resistance of the moving coil of the galvanometer G in Fig. 26.73 is 48.0 ohms, and the galvanometer deflects full scale with a current of 0.0200 A. When the meter is connected to the circuit being measured, one connection is made to the post marked + and the other to the post marked with the desired current range. Find the magnitudes of the resistances R1, R2, and R3 that are required to convert the galvanometer to a multirange ammeter deflecting full scale with currents of 10.0 A, 1.00 A, and 0.100 A.

The picture:

attachment.php?attachmentid=20827&stc=1&d=1254342461.gif


I assume we are looking for the shunt resistor in each case?
Rsh=(Ifs)*(Rc)/(Ia-Ifs)
[
 

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parm09 said:
I assume we are looking for the shunt resistor in each case?
Rsh=(Ifs)*(Rc)/(Ia-Ifs)
[

yes. There are also resistance(s) in series with the meter.
for the 10 A case R2+R3 increase the internal resistance of the galvanometer and R1
is the shunt resistance
 

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