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The radius of two wires of same metal or...

The radius of two wires of same 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,
`f_1:f_2=1:3`
`therefore" "A_1:A_2=pir_1^2:pi_2^2=1:9`
`rArr" "l=(R_1A_1)/L_1=(R_2A_2)/L_2`
`rArr" "A_1/L_1=A_2/L_2" "(thereforeR_1=R_2)`
`rArr" "L_2=(L_1A_2)/A_1`
`=3xx9/1=27m`
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