Calculate the equivalent resistance between the points $A$ and $B$ in the following combination.
Calculate the equivalent resistance between the points $A$ and $B$ in the following combination.
The above circuit can be redrawn as
It is clear that resistances $20 \Omega$ (between $CD)$, $10\, \Omega$ (between $DE)$ and $20\, \Omega$ (between $EF)$ are in a parallel combination. If $R_{1}$ is the effective resistance of all these resistances, then, we have
$\frac{1}{ R _{1}}=\frac{1}{20}+\frac{1}{10}+\frac{1}{20}=\frac{1+2+1}{20}=\frac{4}{20}$
or $\quad R_{1}=5\,ohm.$
Now, the resistors $R _{1}$ and $6 \Omega$ are in series as shown. Therefore, equivalent resistance between $A$ and $B ,$ i.e.
$R=R_{1}+6$
$=5+6=11 \Omega$
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