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:

  1. (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