Question

A piece of wire of resistance ‘r' is uniformly stretched to double the length resistance of wire after starching becomes

Answer 1

As we know that ;
Resistance = Resistivity*length/area
Here we note that the resistance is directly proportional to length and inversely proportional to area of cross section ....
Now a/c to question,;
Length of wire is double then area is reduced to half...
Now
New resistance = resistivity*2length/area/2
New resistance =(resistivity*length/area)*4
New resistance = 4resistance.

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