Question

In metre bridge experiment box(R=2ohom)is Connect in left gap and unknown resistance S in right gap. If balancing length be 50cm calculate value of S?​

Answer 1

Answer:

Null point is found at  l1=40 cm

Using balanced Wheatstone bridge condition,   X2=100−l1l1

∴   X2=100−4040

⟹  X=3Ω

Case 2 :

New null point is found at  l2=50 cm

Using balanced Wheatstone bridge condition,   X′2=100−l2l2

∴   X′2=100−5050

⟹  X′=2Ω

Since the unknown resistance gets decreased, thus we have to connect a resistance R in parallel to X so that X′ comes out to be 2Ω.

Thus resistance of parallel combination  X′=X+RXR

∴   2=3+R3R

⟹  R=6Ω

Hence 6Ω must be connected in parallel to unknown resistance