1.

A wire of resistance `2.20 Omega` has a length `2m`. Calculate the length of the similar wire which connected in parallel with `2m` length wire will give a resistance of `2.0 Omega`

Answer» Correct Answer - `20m`
Resistance per unit length of wire `= 2.2//2 = 1.1 Omegam^(-1)`, Let `R_(1)` be the resistance connected in parallel to `R(=2.20 Omega)` so that effective `R_(P) = 2.0 Omega`. Then
`(1)/(R_(1)) = (1)/(R_(P)) - (1)/(R ) = (1)/(2) - (1)/(2.2) = (0.1)/(2.2) = (1)/(22)`
or `R_(1) = 22 Omega`
`:. ` Length of wire neended `= 22//1 = 20m`


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