Resistance in the two gaps of a meter bridge are $10\, ohm$ and $30\, ohm$ respectively. If the resistances are interchanged the balance point shifts by.............. $cm$
A$33.3$
B$66.67$
C$25$
D$50$
Medium
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D$50$
d (d)$S = \left( {\frac{{100 - l}}{l}} \right).R$
Initially, $30 = \left( {\frac{{100 - l}}{l}} \right) \times 10 \Rightarrow l = 25\,cm$
Finally, $10 = \left( {\frac{{100 - l}}{l}} \right) \times 30 \Rightarrow l = 75\,cm$
So, shift = $50\,cm.$
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