JEE Main 2022 · Physics · Semiconductors and Communication · easy

The unregulated supply is 15 V, the series resistance is 300 Ω and the load resistance across the diode is 600 Ω. The current through the Zener…

Numerical answer

A Zener diode of breakdown voltage

6\ \mathrm{V}

is used as a voltage regulator. The unregulated supply is

15\ \mathrm{V}

, the series resistance is

300\ \Omega

and the load resistance across the diode is

600\ \Omega

. The current through the Zener diode, in mA, is

Show answer and solution

Answer: 20

The Zener holds the voltage across the load at

6\ \mathrm{V}

. Voltage across the series resistor

=15-6=9\ \mathrm{V}

, so the total current is

\dfrac{9}{300}=30\ \mathrm{mA}

. Load current

=\dfrac{6}{600}=10\ \mathrm{mA}

. By Kirchhoff's current law, the Zener current is

I_Z=30-10=20\ \mathrm{mA}

. The series current is fixed by the supply and the Zener voltage, so when the load draws less the diode absorbs the difference.

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