question_answer

Two resistances are connected in two gaps of Meter Bridge. The balance is 10 cm from the zero end. A resistance of 20 \[\Omega \] is connected in series with the smaller of the two. The null point shifts to 20 cm. What is the value of the bigger resistance?

A) 89 \[\Omega \]

B) 144\[\Omega \]

C) 100\[\Omega \]

D) None of the above

Correct Answer: B

Solution :

Option [b] is correct.

Explanation: Case 1: P/Q = 10/90 = 1/9 ...(i)

Case 2: (P+20)/Q = 20/80 = 1/4            ...(ii)

Dividing equation (i) by (ii)

P/(P+20) = 4/9

\[\therefore \]       P = 16 \[\Omega \]

Putting in equation (i) Q=144