Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 311 of 494
A Zener diode exhibits a change in terminal voltage of \( \Delta V_Z = 50\text{ mV} \) when its reverse current changes by \( \Delta I_Z = 10\text{ mA} \). What is the dynamic Zener impedance \( r_z \) of the diode?
A
5.0 Ω
B
0.20 Ω
C
500 Ω
D
50 Ω
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: 5.0 Ω
Concept:

The dynamic Zener impedance \( r_z \) measures how effectively a Zener diode maintains its regulated voltage, and is defined as the ratio of a change in Zener voltage to the resulting change in Zener current.

Formula:

$$r_z = \frac{\Delta V_Z}{\Delta I_Z}$$

Solution:

  • Given: \( \Delta V_Z = 50\text{ mV} = 0.050\text{ V} \) and \( \Delta I_Z = 10\text{ mA} = 0.010\text{ A} \).


  • Dynamic impedance: \( r_z = \frac{0.050\text{ V}}{0.010\text{ A}} = 5.0\ \Omega \).


Why other options are incorrect:

  • Option B: 0.20 Ω is the dynamic conductance \( \Delta I_Z / \Delta V_Z \).
  • Option C: 500 Ω results from an error in unit conversion.
  • Option D: 50 Ω is ten times larger than the calculated value.

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