question_answer

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

A)  \[0.03\,\Omega \]                                         

B)  \[0.3\,\Omega \]

C)  \[0.9\,\Omega \]           

D)         \[0.09\,\Omega \]

Correct Answer: D

Solution :

                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 \[\Rightarrow \]               \[9R=0.81\times 1\] \[\Rightarrow \]               \[R=\frac{0.81}{9}=0.09\Omega \]