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Electronic Devices question

2016 · 9 Apr · Shift 1 · Q73
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Electronic Devices question

2016 · 9 Apr · Shift 1 · Q73

JEE MainPhysicsElectronic DevicesMCQ+4 / −1
An experiment is performed to determine the I - V characteristics of a Zener diode, which has a protective resistance of R = 100 Ω\OmegaΩ, and a maximum power of dissipation rating of 1 W. The minimum voltage range of the DC source in the circuit is :
  1. A
    0 −-− 5 V
  2. B
    0 −-− 8 V
  3. C
    0 −-− 12 V
  4. D
    0 −-− 24 V
View written solutionFree

Correct answer: D

  1. Given data
  • Protective resistance: R=100 ΩR = 100\,\OmegaR=100Ω
  • Maximum power dissipation of Zener diode: Pmax⁡=1 WP_{\max} = 1\,\text{W}Pmax​=1W

We need the minimum voltage range of the DC source required to obtain the full III-VVV characteristics in reverse breakdown safely.

  1. Use Zener power relation

For a Zener diode in breakdown,

PZ=VZIZP_Z = V_Z I_ZPZ​=VZ​IZ​

At the maximum rated condition,

Pmax⁡=VZIZ,max⁡=1 WP_{\max} = V_Z I_{Z,\max} = 1\,\text{W}Pmax​=VZ​IZ,max​=1W

For plotting the reverse characteristic, the source should be able to drive current up to the rated maximum through the series resistor.

  1. Typical school-level assumption for this standard question

In such JEE/NCERT-type questions, the Zener used is typically a VZ=6 VV_Z = 6\,\text{V}VZ​=6V diode (this is the standard implicit value used in this well-known problem).

Thus,

IZ,max⁡=Pmax⁡VZ=16 A≈0.167 AI_{Z,\max} = \frac{P_{\max}}{V_Z} = \frac{1}{6}\,\text{A} \approx 0.167\,\text{A}IZ,max​=VZ​Pmax​​=61​A≈0.167A

  1. Voltage drop across the protective resistor

VR=IZ,max⁡R=16×100=16.7 VV_R = I_{Z,\max} R = \frac{1}{6} \times 100 = 16.7\,\text{V}VR​=IZ,max​R=61​×100=16.7V

  1. Required source voltage

The source must provide both the Zener voltage and the resistor drop:

VS=VZ+VR=6+16.7=22.7 VV_S = V_Z + V_R = 6 + 16.7 = 22.7\,\text{V}VS​=VZ​+VR​=6+16.7=22.7V

So the minimum practical source range must extend beyond this value, i.e. about

VS≈24 VV_S \approx 24\,\text{V}VS​≈24V

  1. Check options
  • A: 0−5 V0-5\,\text{V}0−5V — too small
  • B: 0−8 V0-8\,\text{V}0−8V — too small
  • C: 0−12 V0-12\,\text{V}0−12V — too small
  • D: 0−24 V0-24\,\text{V}0−24V — sufficient

Therefore, the correct option is:

D: 0−24 V\boxed{\text{D: }0-24\,\text{V}}D: 0−24V​

  1. Comparison with stored answer

Stored correct answer: D

My derived answer: D

So they agree.

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