c) AM3 34.72mA AM1 24.69mA VM4 5.47 VM2 5.44V Vs- 12 VM3 6.53V VM1 6.56V AM4 2.0

Question

c) AM3 34.72mA AM1 24.69mA VM4 5.47 VM2 5.44V Vs- 12 VM3 6.53V VM1 6.56V AM4 2.04mAM5 32.67mA AM2 24.69mA It's given that the LED in the above circuit has the following rating: Max voltage across the LED 8V Max Current-25 mA In the above circuit, Zener is connected in series with the LED. Voltmeters are connected to measure the voltage across the LED and the Zener. Ammeters show the current flowing through different nodes. Explain the functionality of the Zener and advice which circuit, out of the two drawn, is the better option and whv.

Explanation / Answer

Zener diodes are widely used as voltage references and as shunt regulators to regulate the voltage across small circuits. When connected in parallel with a variable voltage source so that it is reverse biased, a Zener diode conducts when the voltage reaches the diode's reverse breakdown voltage.

Second circuit is better because resistor used in this circuit in series with LED have higer value(in first circuit 200 ohm and in second circuit 2.5 kohm) so the current flowing through LED is reduced ( in first circuti 24.69mA and 2.04mA in second circuit) and voltage also reduced and LED is protected.

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