Three resistors of resistance \( 15\,\Omega \) each are to be connected in combination. The ratio of maximum equivalent resistance to the minimum equivalent resistance is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 9 : 1 \)
Resistors add in series, which gives the maximum resistance, and their reciprocals add in parallel, which gives the minimum.
\( \displaystyle R_{\max} = 15 + 15 + 15 = 45\,\Omega \)
\( \displaystyle R_{\min} = \frac{15}{3} = 5\,\Omega \)
\( \displaystyle \frac{R_{\max}}{R_{\min}} = \frac{45}{5} = 9 : 1 \)