question_answer

An ammeter reads upto 1 A. Its internal resistance is 0.81\[\Omega .\] To increase die 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 \[9R=0.81\times 1\] \[R=\frac{0.81}{9}=0.09\,\Omega \]