Questions
A cylindrical copper rod is reformed to twice its original length with no change in volume. The resistance between its ends before the change was R Now its resistance will be
detailed solution
Correct option is C
R=ρl1πr12……….(1)Now the rod is reformed such that I2=2I1 and.πr12l1=πr22l2 (No change in volume)or r12/r22=l2/h……..(2)Now R2=ρl2πr22…………(3)From eqs. [1) and (3), we getRR2=l1l2×r22r22=l1l2×l1l2=12×12 [using eq. (2)]∴ R2=4RTalk to our academic expert!
Similar 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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