How to Convert, Galvanometer into a Voltmeter?

It is given in meritnation notes. If you have doubts then ask.

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Conversion into voltmeter: When a suitable high resistance is connected in series with Galvanometer, very negligible current flows through it. By selecting a proper series resistance, we can increase the range of potential to be measured by galvanometer.

if I is the maximum current that gives full deflection, then potential that gives full deflection will be

V = (G + R)I

R is the resistance to be connected in series with galvanometer resistance G

R = (V/I) - G

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Conversion into Ammeter:

When a low resistance called 'shunt' is connected in parallel with Galvanometer, the net resistance becomes smaller and galvanometer gives full deflection for higher values of current.

If we want to measure current I and I_g is the maximum current through galvanometer branch, then the current through parallel shunt wire is I - I_g

potential drop across shunt is equal to potential across galvanometer.

(I - I_g) x S = I_g x G

S = I_g x G / (I - I_g)