Three resistances P, Q, R each of 2Ω and an unknown resistance

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

A balanced wheatstone bridge simply requires

	P	=	R	⇒	2	=	2
	Q		S		2		S

Therefore, S should be 2Ω.
A resistance of 6Ω is connected in parallel.
In parallel combination,

	1	=	1	+	1
	R		R₁		R₂

	1	=	1	+	1
	2		6		s

⇒ S = 3Ω