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## Class 12 Physics (India)

### Course: Class 12 Physics (India)>Unit 14

Lesson 6: Zener diode

# Zener diode voltage regulator

A Zener diode can limit the voltage across it, making it a voltage regulator! In this video, let's explore how a Zener diode can be used to regulate voltage. We are going use it's reverse breakdown characteristics. Created by Mahesh Shenoy.

## Want to join the conversation?

• we see how the zener diode acts as a short, and that is the point of the series resistor to regulate the current. But, if the zener diode acts as a short, would the LED get any current? I guess the zener diode isn't necessarily a short since there is a 2V drop across it. It really isn't a short.
• The zener diode is here so that the excess current can pass through it and not through the LED. To achieve this it must adjust its resistance as low as needed so that overall voltage drop across the parallel connection of the LED and zener diode remains 2V. For infinitely high values of applied voltage it must have infinitely small resistance, in that sense it is a short.
• Why a LED (light emitting diode) bulb has a "diode" at the end?
Is it because of Zener "Diode"?
• LED has not the diode at the end; it is a diode as it name suggests. it emits light when we provide energy to it.
• when the voltage is below 2v the Zener diode will act as an open circuit but won't there be a potential drop across the resistor R's so it will definitely affect the LED's ability to glow right?. And will it not cause an issue in its workings?
• It will and thus should be picked carefully to be provide as little resistance as necessary given the maximum possible voltage.
• why is the LED section is not covered in this module ?
• If the input voltage is above 2v then the resistor blocks that extra voltage and give only 2 voltage to the Zener Diode, right? If so why do we need Zener diode, can't we just directly connect to the LED because of the voltage coming to LED is same as of Zener diode.
• The resistor does not block extra voltage, it take proportional (its own resistance vs resistance of other components) pressure of the applied voltage.

It is here to ensure that when the applied voltage is at the highest, current in the circuit is still within operation limits of the battery.
(1 vote)
• at , we are applying an external resistance in series, to prevent the battery from blowing up. Why can't we attach the resistance in parallel with the Zener Diode? In doing so, the bulb's brightness won't dim.
• The goal here is to keep current in the circuit within operation limits of the battery.

You won't solve this problem by attaching a resistor in parallel: if it's too low, the current will short through it, if it's too high it will be as if it's not here.
(1 vote)
• Mahesh Shenoy continues to provide lucid coverage of all these physics subjects. He is extremely careful not to assume knowledge on the part of us neophyte listeners, whereas other announcers use jargon and terms with which we beginners are not familiar. He also makes sure to provide all details in developing his lecture, and thus provides an understandable explanation. Thank you again, Shenoy, for all your efforts. I'll ask again, if these "India" Physics programs are accessible through regular Khan Academy screens? Seems like I only stumbled on your India talks by Google, and NOT through Khan per se.