Questions
A metallic wire has resistance R. Some part of it is stretched so that its length becomes doubled. Now the resistance of the total wire becomes . The ratio of the lengths of unstretched part and stretched part of initial wire is
detailed solution
Correct option is B
suppose the resistance of the stretched part is R1 and that of unstretched part is R2. then R1+R2 =R------(1)after stretching 4 R1+R2 =4R3 -----(2) if length is doubled resistance becomes 4 timessolving we get 3R1=R3 R1=R9 then R2=89R2R1=81Talk 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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