Question

In the circuit shown the equivalent resistance between $A$ and $B$ is

• A. $27\, \Omega$
• B. $18 \,\Omega$
• C. $90\, \Omega$
• D. $3\,\Omega$

Answer 1

Answer: (D)

$3\,\Omega$

Answer 2

The three resistances between $A$ and $B$ are parallel, $\frac{1}{R_{\text {comb }}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}$ $=\frac{1}{9}+\frac{1}{9}+\frac{1}{9} \frac{1}{R_{\text {comb }}}=\frac{3}{9}$ $\Rightarrow R_{\text {comb }}=3\, \Omega$