JEE Main 2024 Physics question
In a metre-bridge when a resistance in the left gap is 2Ω and unknown resistance in the right gap, the balance length is found to be 40 cm. On shunting the unknown resistance with 2 Ω, the balance length changes by:
Answer: (A)
Solution
2/X = 40/60 ⇒ X = 3 Ω; the shunted value is 3 × 2/5 = 1.2 Ω, so ℓ/(100 − ℓ) = 2/1.2 ⇒ ℓ = 62.5 cm; change = 22.5 cm.