Question

Three resistance P, Q, R each of $2\Omega$ and an unknown resistance S form the four arms of a Wheatstone's bridge circuit. When a resistance of $6\Omega$ is connected in parallel to S the bridge gets balanced. What is the value of S?

• A. $2\Omega$
• B. $3\Omega$
• C. $6\Omega$
• D. $1\Omega$

Answer 1

The correct option is B $3\Omega$

The four resistances of Wheatstone's bridge are $2,2,2$ and $\frac{6s}{6+s}$

In case of a balanced bridge:

$\Rightarrow \frac{2}{2}=\frac{\frac{6s}{6+s}}{2}$

$\Rightarrow \frac{6s}{6+s}=2$

$\Rightarrow 3s=6+s$

$\Rightarrow 2s=6$

$\Rightarrow s=3$ Ohm