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NEETPhysicsCurrent Electricity

In a meter bridge experiment, the left gap contains a resistor of 15 . The right gap contains a 30 resistor connected in parallel with a p-n junction diode. The null point is obtained at 50 cm from the positive end of the meter bridge wire. What is the operating state of the diode and its dynamic resistance?

Options

  1. AReverse biased, infinite resistance
  2. BForward biased, 30
  3. CForward biased, 15
  4. DReverse biased, 30

Correct answer

B. Forward biased, 30

Step-by-step solution

In a meter bridge, the balance condition is given by R_ left R_ right = l 100 - l , where l is the balancing length from the positive end. Given l = 50 cm , the ratio is 50 100 - 50 = 1 . Therefore, the equivalent resistance in the right gap must equal the resistance in the left gap: R_ right = 15 . The right gap contains a 30 resistor in parallel with the diode. Let the dynamic resistance of the diode be R_d . The equivalent resistance is 30 R_d 30 + R_d . Equating this to 15 : 30 R_d 30 + R_d = 15 30 R_d = 450 +

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