Question

a student has a resistance wire of 1ohm. if the length of the wire is 50 cm,to what length he should stretch it uniformly so as to obtain a wire 4ohm resistance

Answer 1

Hy mate

He should stretch the wire up to 200 cm for getting 4 ohm resistanceAs, R = p*I/ATherefore, 1=p*50/AR=>p/A=1/50---(1)Now resistance =4 ohmR=p*I/A4=p*I/AFrom (1)p/A=1/50=> 4=(1/50)I=> I = 200cm

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Answer 2

resistance = 1 ohm
length= 50 cm
area= a (constant)

so,
p= ra/l
p= 1a/ 50 ohm meter

now, resistance= 4 ohm
to find length

r= pl/ a
4= 1a/50×l/a
4= 1/50 l
so, 4×50= l
so, l = 200 cm