Question

What would be the new resistance if length of conductor is doubled and thickness is halved

Answer 1

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l is length at first and A is original area of cross section.

hence,

R~l/A

A=pi*r^2

A’=pi*(r/2)^2

A’=pi*r^2/4=A/4

l’=2l

hence, new resistance, R’

R’=l’/A’

R’=2l/(A/4)

R’=8length/A

R’=8R

New resistance is 8times the original resistance.

Answer 2

new resistance will be 4 times the old resistance becous ;

r~l/a

New R~L/A

R~2l/1/2a

R~4 l/a

but l/a~r

R~4r

this impies new resistance will be 4 time more than before.

hope u find this helpful