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EN17EL301007 Exp3OFC

The document outlines an experiment studying the characteristics of light emitting diodes (LEDs), detailing the apparatus required, theory, working principle, and V-I characteristics. It explains how LEDs emit light when forward biased and provides observations and results from the experiment. Additionally, it includes a self-assessment section with questions about the applications and advantages of LEDs.

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AJINKYA PINDAWALA
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38 views4 pages

EN17EL301007 Exp3OFC

The document outlines an experiment studying the characteristics of light emitting diodes (LEDs), detailing the apparatus required, theory, working principle, and V-I characteristics. It explains how LEDs emit light when forward biased and provides observations and results from the experiment. Additionally, it includes a self-assessment section with questions about the applications and advantages of LEDs.

Uploaded by

AJINKYA PINDAWALA
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Experiment-3

Aim

A study of characteristics of light emitting diode (LED).

Apparatus Required

LED, Ammeter (0-50 mA), Voltmeter (0-10 V), DC power supply, Rheostat

Theory

Definition

A specially doped diode made up of a special type of semiconductors which emits light
when forward biased. It is called as a light emitting diode.
Working principle- The P-N junction emits light when energy is applied on it. The charge
carriers recombine in a forward P-N junction as the electrons cross from the N-region and
recombine with the holes existing in the P-region. Free electrons are in the conduction
band of energy levels, while holes are in the valence energy band. The electrons dissipate
energy by emitting photons.

When the LED is forward biased the free electrons in the N-type material are repelled by
the negative electrode and drawn to the positive electrode. The holes in the P -type
material move the other way. When the voltage difference between the electrodes is high
enough, the electrons in the depletion zone are boosted out of their holes and begin
moving freely again. The depletion zone disappears, and charge moves across the diode.
The interaction between electrons and holes generates light(emits Photons).

V-I Characteristics

The forward bias Voltage-Current (V-I) curve and the output characteristics curve is shown in the figure above.
Circuit diagram

Observation

Forward voltage(v) Forward current(mA)

0.2

0.4

0.6

0.8

Result

1. The LED characteristics are similar to PN junction forward characteristics.


2. The cut-in voltage (the voltage at which conduction begins) for LED is Volts.
Self-Assessment

Q1 Write applications of LED.


Answer: LEDs are used in applications as diverse as aviation lighting,
camera flashes, lighted wallpaper, horticultural grow lights, and medical.

Q2 What are advantages of LED?


Answer
1. The cost of LED’s is less and they are tiny.
2. By using the LED’s the electricity is controlled.
3. The intensity of the LED differs with the help of the microcontroller.

By: Ajinkya Pindawala EN17EL301007

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