physics investigatory project- LDR. IATION ‘N LDR CONCLUSION Based on the obsewation above, it eam be cometuded that the LDR based. INTRODUCTION • A light dependant resistor(LDR) or a photoresistor or photocell . Physics Investigatory Project on LDR as Variable Resistor. Project Report Submitted On Light Dependence Resistance  Submitted By: A. Varun Class â XII Kendriya Vidyalaya no. 2 Pondicherry.

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Teacher Incharge signaturePrincipal signatureExternal signatureAcknowledgements “There are times when silence jnvestigatory so much more loudly than words of praise to only as good as belittle a person, whose words do not express, but only put a veneer over true feelings, which are of gratitude at this point of time. To study the variations, in current flowing in a circuit containing a LDR, because of a variation: In other words, the conductivity goes up.

From 3V approximate 1. The ringing buzzer wards off the intruder and also alerts the neighbors about the intrusion. This is the most common working principle of LDR. For conduction, emitter has some negative voltage in the comparison of pn base.

This circuit saves the men’s power.

DC reaches at base of transistor T 2. Moreover, unique photoresistors may react substantially differently to photons within certain wavelength bands. This project could have been done using a photo-voltaic cell in place of LDR but the circuit would have become complicated in the case of photocell. As a consequence, the collector current of T1 drives transistor T2 and T2 begins to fire.

R, led, battery, transistor and a few resistors. When sufficient base voltage is present, the switch is on. In mines area people face many difficulties due to absence of light in the nights. This puts the relay switch in position-2, which cuts off the buzzer.


These photons in the incident light should have energy greater than the band gap of the semiconductor material to make the electrons jump from investigarory valence band to the conduction band. Ldr Light Dependent Resistor Documents. When a thin slice of p-type is sandwiched between two blocks of n-type, then n-p-n transistor is formed. This extends the scope of the project to the invisible light sources such as ultraviolet and infrared.

It can be used in hilly areas.

Physics Investigatory Project LIGHT DEPENDE Submitted by | Gopinath Sah –

Skip to main content. This type of photoresistor uses a photoconductive material that involves excitation of charge carriers between an impurity and the valence band or conduction band.

Light Dependent Resistance [LDR] is a resistance, in which opposing power of current depends on the presence of quantity of light present, i. Table of observations S.

In frontier and hilly areas, people face many problems due to damaged street lights. But at this time, emitter has some negative voltage in the comparison of its base. Due to use of it, we can solve above problems and can also save electricity and men’s power. In the project, we use relay of 6 ohms. The photoresistor is facing rightwards, and controls whether current flows through the heater which opens the main power contacts.

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Light dependent resistor(LDR) – physics investigatory project

Remember me on this computer. I came to know about many new things. 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. Repeat these steps with different power sources at different distances and note down observations. While the different types of material used for light dependent resistors are semiconductors, when used as a photo-resistor, they are used only as a resistive element and there are no PN junctions.


In project, we use 9-Volt battery. Needless to say, one has also to install a stealth switch that is known only to the owner so that the owner can disable it for his own entry.

By using laser, it can be used for safety purposes. Hence when light having enough energy strikes on the device, more and more electrons are excited to the conduction band which results in large number of charge carriers.

A typical digital counter is shown in the accompanying picture. In mines area people face many difficulties due to absence of light in the nights.

The current will not flow through the LDR and the circuit wont be shunted. Log In Sign Up. Help Center Find new research papers in: Introduction A photoresistor or light-dependent resistor LDR is a light- controlled variable resistor. An opening was cut on the box to present a door. If incident light on a photoresistor exceeds a certain frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band.

One of the most common uses for transistors in an electronic circuit is as simple switches. The intensity decreases as investiggatory distance from the source increases 4. A photoresistor can be applied in light-sensitive detector circuits, and light and dark activated switching circuits. In mines area people face many difficulties due to absence of light in the nights.

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 doesnt glow. It can be used in hilly areas. In de- energized condition, position-1 will be active and in investitatory condition, position-2 will be active.