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3. current electricity — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics3. current electricity1 Mark
MCQ
Under what condition current passing through the resistance $R$ can be increased by short circuiting the battery of emf $E_2$. The internal resistances of the two batteries are $r_1$ and $r_2$ respectively.
  • A
    $E_2r_1 > E_1 (R + r_2)$
  • ✓
    $E_1r_2 > E_2 (R + r_1)$
  • C
    $E_2r_2 > E_1 (R + r_2)$
  • D
    $E_1r_1 > E_2 (R + r_1)$
✓

Answer

Correct option: B.
$E_1r_2 > E_2 (R + r_1)$
b
$\frac{E_{1}}{r_{1}+R}>\frac{E_{2}+E_{1}}{r_{1}+r_{2}+R}$

$E_{1} r_{1}+E_{1} r_{2}+E_{1} R>E_{2} r_{1}+E_{2} R+E_{1} r_{1}+E_{1} R$

$E_{1} r_2 >E_{2}\left(r_{1}+R\right)$

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