A wire of resistance 20 \( \Omega \) is bent to form a complete circle. What will be its resistance between two diametrically opposite points?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 5 \( \Omega \)
Two diametrically opposite points divide the circle into two equal semicircles, each with half the resistance of the wire, and the two are connected in parallel between those points.
\( R_{1} = R_{2} = \frac{20}{2} = 10\,\Omega \)
\( \displaystyle R_{\mathrm{eq}} = \frac{R_{1}R_{2}}{R_{1}+R_{2}} = \frac{10\times10}{10+10} = 5\,\Omega \)