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A metal wire of specific resistance 64xx...

A metal wire of specific resistance `64xx10^(-6) Omega` m and length 1.98 cm has a resistance of `7 Omega`. Find its radius.

Text Solution

Verified by Experts

The correct Answer is:
0.02
With usual notation,
`rho = 64 xx 10^(-6) Omega cm, I = 198 cm, R = 7 Omega`
As `R = rho l/A rArr A = (rho l)/R =((64 xx 10^(-6)) xx 198)/7`
`A =1.8 xx 10^(-3) cm^(2)`
If r is radiu of the wire, `A = pir^(2)`. Thus,
`pir^(2) = 1.8 xx 10^(-3)`
`rArr r = sqrt((1.8 xx 10^(-3))/3.14) = 0.024 cm`
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