Q. 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
A) $33.3\ cm$
B) $66.67\ cm$
C) $25\ cm$
D) $50\ cm$
Explanation
(d) $S = \left( \frac{100 - l}{l} \right).R$
Initially, $30 = \left( \frac{100 - l}{l} \right) \times 10 \Rightarrow l = 25cm$
Finally, $10 = \left( \frac{100 - l}{l} \right) \times 30 \Rightarrow l = 75cm$
So, shift $= 50cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.