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JEE Main 2017 · Physics · Semiconductors and Communication · easy

A 6 V Zener diode is connected in reverse bias across a load of 1 kΩ, in series with a 200 Ω resistor, to a 12 V supply. Assuming the diode is in its…

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A 6 V6\ \mathrm{V} Zener diode is connected in reverse bias across a load of 1 kΩ1\ \mathrm{k\Omega}, in series with a 200 Ω200\ \Omega resistor, to a 12 V12\ \mathrm{V} supply. Assuming the diode is in its breakdown region, the current through the Zener diode is
  1. A. 24 mA24\ \mathrm{mA}
  2. B. 30 mA30\ \mathrm{mA}
  3. C. 6 mA6\ \mathrm{mA}
  4. D. 36 mA36\ \mathrm{mA}
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Answer: (A) 24 mA24\ \mathrm{mA}

The Zener holds the voltage across the load at 6 V6\ \mathrm{V}. The drop across the series resistor is 12−6=6 V12 - 6 = 6\ \mathrm{V}, so the total current is I=6/200=30 mAI = 6/200 = 30\ \mathrm{mA}. The load current is 6 V/1 kΩ=6 mA6\ \mathrm{V}/1\ \mathrm{k\Omega} = 6\ \mathrm{mA}. By Kirchhoff's junction rule the diode current is IZ=30−6=24 mAI_Z = 30 - 6 = 24\ \mathrm{mA}. The value 30 mA30\ \mathrm{mA} ignores the current taken by the load, and 6 mA6\ \mathrm{mA} is the load current itself.
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