Question

The resistance of a 1m long nichrome wire is 6 ohm .if we reduce the length of the wire to 70 cm. What will it's resisy

Answer 1

l=1m

R=6Ω

l'=0.7l

R=ρl'/a=0.7(ρl/a)=0.7R=0.7x6=4.8Ω

Answer 2

Initial length=1m

Intial R=6 ohm

Reduced length=0.7m (converted cm=m)

Formula=S=RA/L

Calculation:R of reduced length R2

L=A (same wire)

R1=L/A R2=L2/A

R1/R2=L1/A=L2/A (A,A gets cut)

R1/R2=L1/L2

R2=L2/L1=R1=6×0.7=4.2 ohm

Therefore R2=4.2 ohm