question_answer

An ammeter A reads 2 A and the voltmeter V reads 20 V. The value of resistance R is (assuming finite resistaneces of ammeter and voltmeter)

A)  exactly 10 \[\Omega \].        

B)  less than 10 \[\Omega \].

C)  more than 10 \[\Omega \].

D)  we cannot definitely say

Correct Answer: B

Solution :

                                \[{{V}_{AB}}=(I-{{I}_{g}})\,.\,\,R={{I}_{g}}\,.\,\,G\] where, G = voltmeter resistance                 \[{{V}_{AB}}=20\,V\]                 \[I=2A\] and \[R=R\]                 \[20=(2-{{I}_{g}})\,.\,\,R\]                 \[R=\frac{20}{2-{{I}_{g}}}\] \[\therefore \] \[R<10\,\,\Omega \]