JEE Advanced 2007 Physics question
A resistance of 2 Ω is connected across one gap of a metre-bridge (the length of the wire is 100 cm) and an unknown resistance, greater than 2 Ω, is connected across the other gap. When these resistances are interchanged, the balance point shifts by 20 cm. Neglecting any corrections, the unknown resistance is
Answer: (A)
Solution
Let the unknown resistance be X (> 2 Ω) and the first balance point be at l cm from the end of the 2 Ω gap: . Since X > 2, l < 50. Interchanging the resistances moves the balance point to 100 − l from the same end, so the
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