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3. current electricity — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics3. current electricity1 Mark
MCQ
Two identical cells each of emf $1.5 \,V$ are connected in parallel across a parallel combination voltmeter connected in the circuit measures $1.2 \,V$.

The internal resistance of each cell is.................$\Omega$

  • A
    $2.5$
  • B
     $4$
  • ✓
    $5$
  • D
    $10$
✓

Answer

Correct option: C.
$5$
c
$V = E - ir / 2$

$1.2=1.5- i \left(\frac{ r }{2}\right)$

$i \frac{ r }{2}=0.3$

$i =\frac{1.5}{10+\frac{ r }{2}} \Rightarrow 10 i +\frac{ ir }{2}=1.5$

$10 i =1.5-0.3$

$i =0.12\, A$

$\Rightarrow r =\frac{0.6}{0.12}=5 \,\Omega$

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