How is a galvanometer converted into a voltmeter?

Explanation

A galvanometer can be converted into a voltmeter by connecting a high resistance in series with it.

In figure,
p.d. across AB is `V=(R+G)I_g`
`R=V/I_g-G`
To convert a galvanometer into a voltmeter , a high resistance is connected in series with the coil. The galvanometer with this modification is called a voltmeter. The value of the high resistance R to be connected in series with the coil depends on the maximum potential difference to be measured . If `I_g` be the current for a full scale deflection then,
`V=I_g(G+R)`
G is the resistance of the galvanometer.

`therefore R=V/I_g-G`
Since G and R are constants , the scale can be graduated to read potential differences directly. A voltmeter is used for measurement of potential difference . It should be connected in parallel in a circuit.