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NEETPhysicsCurrent Electricity

A Wheatstone bridge ABCD has resistors in arms AB , BC , and AD with values 10 , 20 , and 15 respectively. The arm DC contains an unknown resistor R_x in series with a p-n junction diode. A battery is connected across A and C such that A is at a higher potential than C . The galvanometer connected between B and D shows zero deflection. If the diode has a dynamic resistance of 10 in forward bias and infinite resistanc

Options

  1. Ap-side towards D , 20
  2. Bp-side towards C , 20
  3. Cp-side towards D , 30
  4. Dp-side towards C , 30

Correct answer

A. p-side towards D , 20

Step-by-step solution

For a balanced Wheatstone bridge, the ratio of resistances in adjacent arms is equal: R_ AB R_ BC = R_ AD R_ DC . Substituting the given values: 10 20 = 15 R_ DC R_ DC = 30 . The battery is connected across A and C with A at a higher potential. Current flows from A to D to C , meaning the potential at D is higher than the potential at C ( V_D > V_C ). For the diode in arm DC to conduct and offer a finite dynamic resistance, it must be forward-biased. Therefore, its p-side must be connected to the higher potential t

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