Question

A 4ohm wire is double on it .calculate the new resistance of the wire

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class 10 physics

Answer 1

let in First case resistance of wire is R1 and length is l1 ,and after doubling it resistance become r2 and a length be l2.
now., let area of cross section be A1 and A2 respectively........specific resistance be rho!.
now Given ,.
l2= 2* l1,,,.........

see picture!!.
for quick observation....
new resistance = n² * R1.
where n = change in length.like 2times,1/2 times..and ..so on......
so ..here n= 2....
therefore New resistance= 2² *4= 16ohm..
hope it helped you!!