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Multirange Ammeter

  1. Sep 30, 2009 #1
    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)
    [
     

    Attached Files:

  2. jcsd
  3. Sep 30, 2009 #2
    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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