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A wire of length 10 cm and radius 7 10-4 m is connected across the right gap of a meter bridge. When a resistance of 4.5 is connected on the left gap by using a resistance box, the balance length is found to be at 60 cm from the left end. If the resistivity of the wire is R 10-7 , then value of R is :
(3) 66
Balance: 4.5X = 6040 X = 3
X = r2 = X r2
= 3 227 7 10-80.1
= 66 10-7 m
R = 66
Answer: (3)
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