ARYA KAMAL PUBLIC SCHOOL

NAME: ABHISHEK KUMAR

CLASS: XII Non Medical
ROLL no. :
SESSION: 2023-24
SUBJECT: PHYSICS

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 CERTIFICATE
This is to certify that Student Name Shrey
Chauhan has successfully completed his
Physics project titled
ELECTROMAGNETIC INDUCTION
under the supervision and guidance of
Physics Teacher Mr. PRAVEEN
in the partial fulfillment of the
Physics practical assessment conducted
during the academic year
2023-2024.
EXAMINER TEACHER

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 AKNOWLEDGEMENT
I would like to express my immense
gratitude to my physics teacher Mr.Praveen
for help and guidance he provided for
completing this project.I also thank my
parents who gave their ideas and inputs in
making this project. Most of all I thank our
school management, for providing us the
facilities and opportunity to do this
project.Lastly, I would like to thanks my
classmates who have done this project
along with me. Their support made this
project fruitful.
STUDENT NAME- SHREY CHAUHAN

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 INDEX

INTRODUCTION

PRINCIPLE

THEORY

WORKING&CONSTRUCTION

APPLICATIONS

OBSERVATION

CONCLUSION

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 INTRODUCTION
In the society, sometimes street lights glow in day time due
to any reason. In mines area people face many difficulties
due to absence of light in the nights. In frontier and hilly
areas, people face many problems due to damaged street
lights. For solve above these problems, we create a device in
which the lights glow in night and in day time, they off
automatically and don't glow. Due to use of it, we can solve
above problems and can also save electricity and men's
power.

PRINCIPLE

This project is based on Light Dependent Resistance

(L.D.R.).LDR is a resistance, in which opposing power of
current depends on the presence of quantity of light
present, i.e. the resistance of LDR increases or decreases,
according to quantity of light which falls on it. If LDR places
in darkness, the resistance of LDR increases and when light
falls on it, the resistance of LDR decreases and act as a
conductor. Any LDR in the presence of light and darkness
changes its resistance is depending on the different types of
LDR.

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BRIEF DISCRIPTION OF
COMPONENTS

⦁ TRANSISTOR: When a thin slice of p-type is

sandwiched between two blocks of n-type, then n-p-n
transistor is formed. It consists of emitter, base, and
collector. In the project, common emitter n-p-n
transistor (BC-547) is used.

⦁ CARBON RESISTOR: A carbon resistor has generally

four rings or bands A, B, C and D of different colours
corresponding to the value of resistance. In project, we
use carbon resistance of two 100 kilo-ohms, 470 ohms
and 330 ohms.

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⦁ LDR: LDR means light dependent resistance which
is used to complete the circuit.

⦁ LED: A light-emitting diode (LED) is a semiconductor

light source. When a light-emitting diode is forward-
biased (switched on), electrons are able to recombine
with electron holes within the device, releasing energy
in the form of photons. In this project, we use led of
white colour.

⦁ BATTERY: This is a rectangular prism shape with

rounded edges and a polarized snap connector at the

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top. In project, we use 9-Volt battery.

⦁ WIRES: A wire is a single, usually cylindrical, flexible

strand or rod of metal. These are used to connect
components.

Aim

⦁ Dark sensor using L.D.R, led, battery, transistor

and a few resistors.

⦁ Light sensor using L.D.R, led, battery, transistor

and a few resistors.

Circuit Diagram
⦁ Dark Sensor

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⦁ Light Sensor

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WORKING
(a) Dark Sensor

Let 9V-DC is flowed in the circuit. When light falls on LDR

then the resistance of LDR will decrease and
approximate equal to 10 ohms. 9V DC comes from 330
10
ohms resistance and passes through an LED to the
collector end of the BC-547 transistor. Also 9V DC comes
though a 100 kilo-ohms resistance to one end of LDR and
to the base of the transistor. When DC voltage comes
through the base of transistor, the current starts to flow
through the emitter of transistor and completes the
circuit to the negative end of the DC voltage. Another
end of the 100 kilo- ohms resistor is connected to the
emitter. When light falls on the LDR, the resistance
offered by the LDR is very high (nearly millions). The
current will not flow through the LDR and the circuit
won’t be shunted. Therefore the circuit is complete
through the 100 kilo-ohms resistor and the led will glow.
When no light falls on the LDR, the LDR offers very low
resistance (nearly 10 ohms) and the circuit is shunted
and therefore the led doesn’t glow. The LDR is also
connected to minimise the current flow to the battery.

USES

⦁ It can be used in street lights.

⦁ It can be used in mines areas.

⦁ It can be used in hilly areas.

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⦁ It can be used in frontier areas.

⦁ It can be used in houses.

⦁ It can be used in jail lights.

⦁ By using laser, it can be used for safety purposes.

(b) Light Sensor

Let 9V-DC is flowed in the circuit. When light falls on LDR

then the resistance of LDR will decrease and
approximate equal to 10 ohms. 9V DC comes from 470
ohms resistance and passes through an LED to the
collector end of the BC-547 transistor. Also 9V DC
comes though one end of LDR and the other end to
100 kilo-ohms and to the base of the transistor. When
DC voltage comes through the base of transistor,
current starts to flow through the emitter of transistor
and completes the circuit to the negative end of the DC
voltage. Another end of the LDR is connected to the
emitter. When light falls on the LDR, the resistance
offered by the LDR is very high (nearly millions).
Therefore the circuit is not complete and the led will not
glow. When no light falls on the LDR, the LDR offers very
low resistance (nearly 10 ohms) and therefore the led
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glows. The 100 kilo-ohms is connected to minimise the
current flow to the battery.

USES

⦁ By using laser, it can be used for safety purposes.

⦁ It can be used to find the intensity of sunlight

falling on the LDR.

⦁ It can be used in mines areas for current

indicator using another light.

⦁ It can be used in hilly areas.

⦁ It can be used in houses.

⦁ By using buzzer, it can be used for security purposes in

jails.

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 Conclusion

A darkness detector circuit using LDR is a very simple

circuit which can have many applications in the real world.
This project requires very few components and is a cool
system for your first electronics project. You can use this
circuit as a subsystem and integrate it in your future
projects

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