Computing the value of a shunt resistor

Question: Determine shunt resistance needed to convert a galvanometer to an ammeter with a full scale reading of 10 A if the scale requires 2.5 mA to cause full scale deflection with a coil resistance of 10 ohms?

Answer:

I original meter max = I full scale deflection = 2.5 mA
Using the current divider principle:
(I original meter max)/(I adjusted meter max)=(R shunt)/(R meter + R shunt)
(25 mA) / (10 A) = (R shunt) / (10 ohms + R shunt)
R shunt =  0.0251 ohms

Use of a Shunt Resistor

Question: What device is used to extend the range of a DC ammeter and how is it connected to the basic meter?


Answer:

A resistor connected in parallel or shunt to the ammeter can be used to extend the ammeter's range.