Discussion
The difference between maximum and minimum resistance that can be obtained by connecting three resistances of \(\frac{1}{3}\ \Omega\) each is :
Answer: B
The difference is \(\frac{8}{9}\ \Omega\).
The maximum resistance comes from connecting all three in series and the minimum from connecting all three in parallel:
\[ \begin{aligned} R_{max} &= 3 \times \tfrac{1}{3} = 1\ \Omega \\ \frac{1}{R_{min}} &= 3 + 3 + 3 = 9 \Rightarrow R_{min} = \tfrac{1}{9}\ \Omega \\ R_{max} - R_{min} &= 1 - \tfrac{1}{9} = \tfrac{8}{9}\ \Omega \end{aligned} \]
1 Ω and 1/9 Ω are the maximum and minimum themselves, not their difference, and 2/3 Ω does not follow from either arrangement.
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