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A wire of resistance is stretched to twice its original length. The resistance of stretched wire would be
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Correct option is B
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 UsingiSimilar Questions
In an electrical cable there is a single wire of radius 9 mm of copper. Its resistance is 5Ω . The cable is replaced by 6 different insulated copper wires, the radius of each wire is 3 mm . Now the total resistance of the cable will be
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