# Multirange Ammeter

1. Sep 30, 2009

### parm09

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:

I assume we are looking for the shunt resistor in each case?
Rsh=(Ifs)*(Rc)/(Ia-Ifs)
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2. Sep 30, 2009

### willem2

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