Question

Question 7
What is the minimum resistance which can be made using five resistors each of $\frac{1}{5}\Omega$?

(a) $\frac{1}{5}\Omega$
(b) $\frac{1}{25}\Omega$
(c) $\frac{1}{10}\Omega$
(d) $25\Omega$

Answer 1

(b) $\frac{1}{25}\Omega$

Minimum resistance will be achieved when all the resistors are connected in parallel.
$\frac{1}{R_{min}}=(\frac{1}{\frac{1}{5}}+\frac{1}{\frac{1}{5}}+\frac{1}{\frac{1}{5}}+\frac{1}{\frac{1}{5}}+\frac{1}{\frac{1}{5}})$
$\Rightarrow$ $\frac{1}{R_{min}}=5+5+5+5+5=25$
$\Rightarrow$ $R_{min}=\frac{1}{25}\Omega$