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resistance of wire of length 10 cm is 2 ohm if the wire is stretched uniformly of 40 cm the resistance is

resistance of wire of length 10 cm is 2 ohm if the wire is stretched uniformly of 40 cm the resistance is 

Grade:12

1 Answers

Arun
25750 Points
5 years ago
The length (L) increases 5 times to L' = 4L. 

Since the volume of metal will be constant, the cross-sectional area (A) is reduced to A' = A/4. 

The new resistance (R') is: 
R' = ρL'/A' 
. . = ρ(4L)/(A/4) 
. . = 16ρL/A 
. . = 16R 

So resistance increases 16 times, from 2 ohms to 2 x 16 = 32 ohms.

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