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STD 12 - 3. current electricity — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 12 - 3. current electricity4 Marks
MCQ
ln a balanced wheat stone bridge, current in the galvanometer is zero. It remains zero when:

$[1]$ battery emf is increased

$[2]$ all resistances are increased by $10\,ohms$

$[3]$ all resistances are made five times

$[4]$ the battery and the galvanometer are interchanged

  • A
    only $[1]$ is correct
  • B
    $[1], [2]$ and $[3]$ are correct
  • ✓
    $[1], [3]$ and $[4]$ are correct
  • D
    $[1]$ and $[3]$ are correct
✓

Answer

Correct option: C.
$[1], [3]$ and $[4]$ are correct
c
For wheatstone bridge,

It is independent of emf Let $r=K R$

$\Rightarrow \mathrm{r}_{1} \mathrm{r}_{4}=\mathrm{K}^{2}\left(\mathrm{R}_{1} \mathrm{R}_{4}\right)=\mathrm{K}^{2}\left(\mathrm{R}_{2} \mathrm{R}_{3}\right)=\mathrm{r}_{2} \mathrm{r}_{3}$

So it is still balance Even if battery and galvanometer are interchanged, still it is balanced. $(1)$ $(3),$ $(4)$ are true, hence.

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