Question

In Wheatstone's bridge $P=9$ ohm, $Q=11$ ohm, $R=4$ ohm and $S=6$ ohm. How much resistance must be put in parallel to the resistance $S$ to balance the bridge

• A. $24ohm$
• B. $\frac{44}{9}ohm$
• C. $26.4ohm$
• D. $18.7ohm$

Answer 1

Answer: (C)

$26.4ohm$

For wheat stone bridge we knwo $\frac{P}{Q}=\frac{R}{S^{{}^{\prime }}}$ (For balancing bridge)

$\Rightarrow S^{{}^{\prime }}=\frac{4\times 11}{9}=\frac{44}{9}$

$\Rightarrow \frac{1}{S^{{}^{\prime }}}=\frac{1}{r}+\frac{1}{6}$

$\Rightarrow \frac{9}{44}-\frac{1}{6}=\frac{1}{r}$

$\Rightarrow r=\frac{132}{5}=26.4\Omega$