question_answer

An ammeter reads upto 1 A. Its internal resistance is \[0.81\,\,\Omega \]. To increase the range to 10 A, the value of the required shunt is [AIEEE 2003]

A) \[0.03\,\,\Omega \]

B) \[0.3\,\,\Omega \]

C) \[0.9\,\,\Omega \]

D) \[0.09\,\,\Omega \]

Correct Answer: D

Solution :

[d] To increase the range of ammeter we have to connect a small resistance in parallel (shunt), let its value be R.

Apply KCL at junction to divide the current:

Voltage across R

= Voltage across ammeter

\[\Rightarrow 9R=0.81\times 1\]

\[\Rightarrow R=\frac{0.81}{9}=0.09\,\,\Omega \]