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The radius of two wires of saine metal o...

The radius of two wires of saine metal ore in the ratio of 1 : 3 and their resistance are equal. If the length of first wire is 3 m then length of second 'wire is

A

3 m

B

9 m

C

27 m

D

1 m

Text Solution

Verified by Experts

The correct Answer is:
C
According to question,
`r_(1):r_(2)=1:3`
`:. A_(1):A_(2)= pi r_(1)^(2) : pi_(2)^(2)=1:9`
`rArr 1=(R_(1)A_(1))/(L_(1))=(R_(2)A_(2))/(L_(2))`
`rArr (A_(1))/(L_(1))=(A_(2))/(L_(2))" " ( :. R_(1)=R_(2))`
`rArr L_(2)=(L_(1)A_(2))/(A_(1))`
`3xx(9)/(1)=27m`
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