IIT JEE Advanced 2010 Paper 1

Since an ammeter is connected in series to measure the current, its resistance should be as small as possible. Hence, a very low shunt resistance (R2) is put in parallel to the galvanometer so that the
Req =

RgR2

Rg+R2

= R2
where R2 is the resistance of the galvanometer. Since a voltmeter is put in parallel to measure the voltage, its resistance should be as high as possible. Hence, a high resistance (R1) is put in series with the galvanometer so that
Req = Rg+R1 = R1