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NEETPhysicsCurrent Electricity

A student is performing an experiment using a metre bridge to determine the value of an unknown resistance. To ensure the most accurate measurement and minimize percentage errors, the student should choose the standard resistance from the resistance box such that the null point is obtained:

Options

  1. Anear the 10 cm mark on the wire.
  2. Bnear the 90 cm mark on the wire.
  3. Cat any position, as the accuracy is independent of the null point location.
  4. Dnear the 50 cm mark on the wire.

Correct answer

D. near the 50 cm mark on the wire.

Step-by-step solution

In a metre bridge, the two segments of the wire act as the ratio arms of the Wheatstone bridge. The sensitivity of the bridge is maximum and the percentage error in the measurement is minimum when all four arms have resistances of the same order of magnitude. This condition is satisfied when the balancing length is near the middle of the wire (around 50 cm ). Additionally, measuring near the middle minimizes the effect of end resistances caused by the copper strips and connecting wires, which would otherwise introd

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