Question:
The circuit shown below is working as a 8 V dc regulated voltage source. When 12 V is used as input, the power dissipated (in mW) in each diode is; (considering both zener diodes are identical) _________.
The circuit shown below is working as a 8 V dc regulated voltage source. When 12 V is used as input, the power dissipated (in mW) in each diode is; (considering both zener diodes are identical) _________.
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Two identical Zener diodes in series regulate 8 V, so each holds 4 V. The current through the two 200 \(\Omega\) series resistors is \((12 - 8)/400\).
Updated On: Nov 5, 2026
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Correct Answer: 40
Solution and Explanation
The two identical Zener diodes are in series across the output, which is regulated at 8 V, so each Zener has 4 V across it.
The two 200 \(\Omega\) resistors in series drop \(12 - 8 = 4\) V, so \(I = \frac{4}{400} = 10\) mA. The output is open (no load), so this entire current flows through the diodes.
Power in each diode: \(P = V_ZI = 4\times 10\times 10^{-3}\) W = 40 mW.
Answer: 40
The two 200 \(\Omega\) resistors in series drop \(12 - 8 = 4\) V, so \(I = \frac{4}{400} = 10\) mA. The output is open (no load), so this entire current flows through the diodes.
Power in each diode: \(P = V_ZI = 4\times 10\times 10^{-3}\) W = 40 mW.
Answer: 40
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