A wire of resistance 4 Ω is stretched to twice its original length. The resistance of stretched wire would be

Resistance of a wire,R=ρ1A=4Ω         −−−iWhen wire is stretched twice, its new length be ‘l’. Then l'=2lOn stretching volume of the wire remains constant.∴  lA=l'A'where A'  is the new cross-sectional area Or A'=1l'A=12lA=A2∴ Resistance of a stretched wire is R'=ρl'A'=ρ2lA/2=4ρlA=44Ω=16Ω                                     Usingi