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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How a light dependent resistor LDR works Documents.

They gave me different ideas in making this project unique. In project, we use carbon resistance of two kilo-ohms, ohms and ohms.

Light dependent resistor(LDR) – physics investigatory project

The error lies within the experimental limit. It can be used to find the intensity of sunlight falling on the LDR. In this project, we use led of white colour. Theory Alight dependent resistor works on the principle of photo conductivity.

A photoresistor can be applied in light-sensitive projectt circuits, and light and dark activated switching circuits.

As a consequence, the collector current of T1 drives transistor T2 and T2 begins invsetigatory fire. Another end of the LDR is connected to the emitter. Anti-theft alarm for Banks and offices. Distance between Source Bulb S.

There is an increase in the current as the distance from the source decreases. In project, we use carbon resistance of kilo-ohms, 1.

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. In the project, INdiode is used. LDR is a resistor whose resistance decreases with increasing incident light intensity. Thus, when there is no light on the LDR, the transistor remains un-fired.

For this, we have to simply projecg the buzzer with a digital counter. The relay has two positions. A photoresistor is made of a high resistance semiconductor.


The LDR may not be perpendicular to the source. Similarly switch to current section and move to micro ampere in the multimeter. This intruder alarm can be easily set up in houses, banks, schools etc. Help Center Find new research papers in: This is a rectangular prism shape with rounded edges and a polarized snap ln at the top. When a thin slice of p-type is sandwiched between two blocks of n-type, then n-p-n transistor is formed.

They are also used in some dynamic compressors together with a small incandescent or neon lamp, or light-emitting diode to control gain reduction. Another end of the kilo-ohms resistor is connected to the emitter.

Therefore the circuit is complete through the kilo-ohms resistor and the led will investigatpry. From 3V approximate 1.

The resistance of a photoresistor decreases with increasing invfstigatory light intensity; in other words, it exhibits Photoconductivity. When DC voltage comes through the base of transistor, the current starts to flow through the emitter of transistor and investigatoru the circuit to the negative end of the DC voltage.

At this time, it becomes earth, so that no voltage flows through the base of transistor T 1. But at this time, 4V DC reach at base of transistor T 2so that emitter has highly negative voltage in comparison of its base, so that transistor T 2 highly conducts.

Although we have used a low intensity laser, this can be harmful if aimed accidently at the eyes or if the reflected beam is seen through naked eye.

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

Physics Investigatory Project LIGHT DEPENDE Submitted by | Gopinath Sah –

Light source white, ultra-violet and laser 2. 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.


The collector current of T2 is now large enough to energize the relay. I came to know about many new things. Choose a specific position for the source and mount it using a holder, make sure it is stable. The LDR is also connected to minimise the current flow to the battery.

Physics Investigatory Project On LDR | Richard Parker –

Unlike photocells, LDRs, do not generate electricity but only change their conductivity. Enter the email address you signed up with and we’ll email you a investigztory link.

The advantage is that; we can dupe the intruder by using invisible light as the light rays will not be visible even in the night. Page 13 of 23 Photoresistors can be placed in streetlights to control when the light is on.

Photo resistors have been seen in early forms since the nineteenth century when photoconductivity in selenium was discovered by Smith in The result of this process is more and more current starts flowing through the device when the circuit is closed and hence it is said that the resistance of the device has been decreased.

So, whenever, light is interrupted, the relay goes to position-1 where, the buzzer is connected and the buzzer starts ringing. Much useful work was conducted by T. But at this time, emitter has some negative voltage in the comparison of its base. By using laser, it can be used for safety purposes.

A typical digital counter is shown in the accompanying picture.