JEE Main · 2006 · 30 Apr 2006 · Offline · Current Electricity

In a Wheatstone's bridge, there resistances P, Q and R connected in the three arms and the fourth arm is formed by two resistances

S_{1}

and

S_{2}

connected in parallel. The condition for bridge to be balanced will be

Answer: (C)

Solution

A Wheatstone bridge is balanced when its arms satisfy

\frac{P}{Q} = \frac{R}{S}

, where

S

is the fourth-arm resistance. Here the fourth arm is two resistances in parallel,

S = \frac{S _{1} S _{2}}{S _{1} + S _{2}}

. Putting this in, the balance condition becomes

\frac{P}{Q} = \frac{R}{S _{1} S _{2} / ( S _{1} + S _{2} )} = \frac{R ( S _{1} + S _{2} )}{S _{1} S _{2}}

JEE Main · 2006 · 30 Apr 2006 · Offline · Single correct option