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Engineering Entrance Exams

A wire of resistance 5 O is drawn out so that its new length is 3 times its original length.What is the reistance of the new wire? (A) 45 O (B) 15 O (C) 5/3 O (D) 5 O

Profile image of Ashwani sinha
12 Years agoGrade
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2 Answers

Profile image of Saurabh Koranglekar
6 Years ago
Dear student

R = (rho)l/a

volume =l*a = constant

Now you can calculate

Regards
Profile image of Vikas TU
6 Years ago

By stretch the wire till its length is triple while the volume remains constant, the cross sectional area is three times less compared to its original value.

Therefore, when you computed the ratio between the original and the new value of the resistance, it would be:

R/R' = (L/A) / (L'/A') = 1/9
Thus, the new resistance would be R' = 9R = 45O


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