Questions
A wire has a resistance 10 . It is stretched by one-tenth of its original length. Then its resistance will be
detailed solution
Correct option is B
Here volume remains constant. Thusπr12l=πr22(11l/10)or πr22=1011πr12{ ∴When wire is stretched by 1/10 of its original length, the new length of wire becomes (11 / / 10)}Let the new resistance be R2. ThenR2=ρ⋅1110lπr22=(11/10)ρl(10/11)πr12=(11/10)10/11)ρlπr12=(11/10)(10/11)×10=12110=12⋅1ΩTalk to our academic expert!
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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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