# Q. 1.     A piece of wire of resistance $R$ is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is $R'$, then the ratio $R/R'$ is –              (a) 1/25             (b) 1/5             (c) 5             (d) 25

Given: A piece of wire of resistance $R$ is cut into five equal parts.

Resistance of each part is $\frac{R}{5}$.

$\frac{1}{R'}=\frac{5}{R}+\frac{5}{R}+\frac{5}{R}+\frac{5}{R}+\frac{5}{R}$

$\frac{1}{R'}=\frac{25}{R}$

$R'=\frac{R}{25}$

Hence, $\frac{R}{R'}=\frac{R}{\frac{R}{25}}=25$

Thus, option D is correct.

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