question_answer

An ammeter A reads \[\text{2 A}\] and the voltmeter \[V\] reads\[\text{2}0\text{ V}\]. 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 \[{{V}_{AB}}=20V\] \[I=2A\] and \[R=R\] \[20=(2-{{I}_{g}}).R\] \[R=\frac{20}{2-{{I}_{g}}}\] \[\therefore \]  \[R<10\Omega \]