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Two unknown resistance are connected in the two gaps of a meter-bridge. The null point is obtained at 40 cm from the left end. A 30 Ω resistance is connected in series with the smaller of the two resistances, the null point shifts by 20 cm to the right end. What is the value of the smaller resistance (in Ω )?

Correct answer

24

Step-by-step solution

l x = 40   c m ,   l R = 60   c m x R = l x l R = 40 60 = 2 3 ....... (i) ∴           x + 30   R = 60 40 = 3 2 ∴       x + 30 x = 9 4 9 x = 4 x + 120 5 x = 120     ⇒     x = 24   Ω

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