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a wire of resistance 5 ohm is drawn out to its new length, three times its original length. the resistance of new wire is..

a wire of resistance 5 ohm is drawn out to its new length, three times its original length. the resistance of new wire is..

Grade:12

2 Answers

Saurabh Koranglekar
askIITians Faculty 10335 Points
4 years ago
Dear student

R =þ * l / A

Volume is constant

l *A = 3 l * A/3

So

5 =þ l/A
Rnew = 9 * 5 = 45 ohms

Regards
Vikas TU
14149 Points
4 years ago
Dear student 
R1 = 5 ohm 
l1 = l 
l2 = 2l
When wire is stretched V1 = V2 
A1l1 = A2l2 
A2 = A1/2
R1/R2 = 1/4 
R2 = 4R1
 

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