1.

In an electrical cable there is a single wire of radius `9 mm` of copper. Its resistance is `5 Omega`. The cable is replaced by 6 different insulated copper, wires the radius of each wire is `3 mm`. Now the total resistance of the cable will beA. `7.5 Omega`B. `5.5 Omega`C. `6Omega`D. `8Omega`

Answer» Correct Answer - A
Resistance of 9 mm cable is `5 Omega` .
Now,`R prop (1)/(A) :.R prop (1)/(r^(2))`
`:.` Resistance of 3 mm cable `= 9 xx 5 = 45 Omega`.
In second case, six wires are connected in parallel.
Thus, its resistance is given by,
`R_(p)=(45)/(6)=7.5Omega`.


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