CBSE Class 12-science Answered

(a) Balance point from end A, l₁ = 39.5 cm

Resistance of the resistor Y = 12.5 Ω

Condition for the balance is given as,

 X/Y = (100 - l₁ )/ l₁

X =[ (100 - 39.5)/39.5] x12.5 = 8.2 Ω

Therefore, the resistance of resistor X is 8.2 Ω.

The connection between resistors in a Wheatstone or metre bridge is made of thick copper strips to minimize the resistance, which is not taken into consideration in the bridge formula.

(b) If X and Y are interchanged, then l₁ and 100−l₁ get interchanged.

The balance point of the bridge will be 100−l₁ from A.

100−l₁ = 100 − 39.5 = 60.5 cm

Therefore, the balance point is 60.5 cm from A.

Hope this clarifies your doubt.

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