Moving Charges and Magnetism - Result Question 76
78. A milli voltmeter of 25 milli volt range is to be converted into an ammeter of 25 ampere range. The value (in ohm) of necessary shunt will be :
[2012]
(a) 0.001
(b) 0.01
(c) 1
(d) 0.05
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Answer:
Correct Answer: 78. (a)
Solution:
- (a) Galvanometer is converted into ammeter, by connected a shunt, in parallel with it.
$\frac{G S}{G+S}=\frac{V_G}{I}=\frac{25 \times 10^{-3}}{25}$
$\frac{G S}{G+S}=0.001 \Omega$
Here $S«G$ so
$S=0.001 \Omega$
In order to increase the range of ammeter $n$ times, the value of shunt resistance to be connected in parallel to galvanometer is
$ S=\frac{G}{n-1} $
Here, $G=$ resistance of galvanometer
