(a) Briefly explain how a galvanometer is converted into a voltmeter.

(b) A voltmeter of a certain range is constructed by connecting a resistance of 980\; \Omega in series with a galvanometer. When the resistance of 470\; \Omega is connected in series, the range gets halved. Find the resistance of the galvanometer.

 

 

 
 
 
 
 

Answers (1)
S safeer

(a) A galvanometer can be converted into Voltmeter by connecting a high-value resistance R in series with the coil of the galvanometer. The value of (R) is related to the maximum voltage (V) to be measured as

 R=\frac{v}{I_{g}}-G

(b) To determine the resistance of the galvanometer :

    We have, I_{g}=\frac{v}{R_{g}+R}

Where, R_{g}= Resistance of a galvanometer

              I_{g}= Current in galvanometer 

Now, According to the Question,

        \frac{V}{R_{g}+980}=\frac{V}{2(R_{g}+470)}

therefore, 2R_{g}+940=R_{g}+980

Hence,     R_{g}=40\; \Omega

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