JEE Mains · Physics · STD 12 - Current electricity
- JEE Mains 2017
- Hard
- MCQ
A \(9\, V\) battery with internal resistance of \(0.5\,\Omega \) is connected across an infinite network as shown in the figure. All ammeters \(A_1 , A_2, A_3\) and voltmeter \(V\) are ideal. Choose correct statement

Pick an option to check your answer.
Answer & Solution
Correct Answer
(A) Reading of \(A_1\) is \(2\,A\)
Step-by-step Solution
Detailed explanation
The given circuit can be redrawn as,
as \(4\, \Omega\) and \(x \,\Omega\) are parallel
\(x^{\prime}=\frac{1}{4}+\frac{1}{x}=\frac{(4+x)}{4 x} \quad x^{\prime}=\frac{4 x}{4+x}\)
and \( 1 \,\Omega\) and \(1\, \Omega\) are also in series \(x^{\prime \prime}=2\, \Omega\) Now equivalent resistance of circuit
\(x=\frac{4 x}{4+x}+2=\frac{8+6 x}{4+x}\)
\(4 x+x^{2}=8+6 x\)
\(x^{2}-2 x-8=0\)
\(x=\frac{2 \pm \sqrt{4-4(1)(-8)}}{2}=\frac{2 \pm \sqrt{36}}{2}\)
\(=\frac{2 \pm 6}{2}=4\, \Omega\)
Reading of Ammeter \(A_{1}=\frac{V}{(R+r)}\)
\(A_{1}=\frac{9}{4+0.5}=2\) \(Ampere\)
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