Question
A given galvanometer is to be converted into (i) an ammeter (ii) a milliammeter (iii) a voltmeter. In which case will the required resistance be (i) least (ii) highest and why?

Answer

The required resistance has least value in the case of an ammeter and maximum value in the case of a voltmeter.
This is due to the reason that the shunt resistance required to convert a galvanometer into ammeter or milliammeter has the value.
$\text{S}=\frac{\text{I}_g}{\text{I}-\text{I}_\text{g}}\times\text{R}_\text{g}$
Thus, the shunt required in the case of milliammeter has higher value.
Similarly, since the voltmeter should have a high resistance, the value of required resistance should be highest in the case of a voltmeter. This is connected in series with the coil of the galvanometer.

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