**Lecture Notes :- **

**Q. A galvanometer with a full scale current of 10mA has a resistance of 1000Ω. The multiplying power (the ratio of measured current togalvanometer current) of 100Ω shunt with this galvanometer is [2004]**

**(a) 110**

**(b) 100**

**(c) 11**

**(d) 10**

**Ans. **

**Given :-** I_{fs} = I_{m} = 10 mA

R_{m }= 1000 **Ω**

R_{sh} = 100 **Ω**

m= ?

**Solution :- **The formula for calculating multiplying factor is given by,

m= measured current / galvanometer current = I/I_{m}

I_{sh} R_{sh} = I_{m} R_{m} —-(i)

I = I_{m }+ I_{sh }

I_{sh }= I – I_{m}

(I-I_{m}) R_{sh} = I_{m} R_{m}

IR_{sh} – I_{m} R_{sh} = I_{m} R_{m}

IR_{sh }= I_{m} R_{sh} + I_{m} R_{m }

IR_{sh} = I_{m} (R_{sh} + R_{m})

Therefore, option (c) is the correct answer.

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