Q.Three resistors $R_1 = 2\ \Omega$, $R_2 = 3\ \Omega$ and $R_3 = 6\ \Omega$ are available. Find the equivalent resistance when they are connected

Given $R_1=2\ \Omega$, $R_2=3\ \Omega$, $R_3=6\ \Omega$.

1. All in series:

   $R_s = R_1+R_2+R_3 = 2+3+6 = 11\ \Omega$

2. All in parallel:

   $\frac{1}{R_p} = \frac{1}{2}+\frac{1}{3}+\frac{1}{6} = \frac{3+2+1}{6} = \frac{6}{6}=1 \ \Rightarrow\ R_p = 1\ \Omega$

   (c) $R_2$, $R_3$ in parallel, then in series with $R_1$: …

Apply $R_s=\sum R_i$ for series and $1/R_p=\sum 1/R_i$ for parallel; for the mixed case, reduce the paral …

• Adding resistances directly for a parallel combination instead of adding their reciprocals.
• In part (c), combining $R_1$ with $R_2$ or $R_3$ first instead of correctly combining $R_2$ …