question_answer

In a Wheatstone bridge (see fig), Resistances P and Q are approximately equal. When \[R=400\Omega ,\]the bridge is balanced. On interchanging P and Q, the value of R, for balance, is \[405\Omega ,\]The value of X is  close to-

[JEE Main 11-Jan-2019 Morning]

A) 401.5 ohm

B) 404.5 ohm

C) 403.5 ohm

D) 402.5 ohm

Correct Answer: D

Solution :

[d] For a balanced bridge,          ...(i)

After interchanging P and Q,       ...(ii)

Multiplying both the equations,