Part of The Student Room Group

  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Investigation of a light dependant resistor.

Extracts from this document...

Introduction

Investigation of a light dependant resistor

Light dependant resistors or LDRs are resistors which alter their resistivity according to a particular light level. I am going to find out how these work and use them in a context so I can use them to locate a light source. To do this I must firstly find out how light effects the LDRs and then use this data to try and create something in order to detect a light source and locate it.

Results

Distance light is away from LDR

  Voltage reading (supply-12v)                  

5cm

11.5

10cm

10.9

15cm

8.7

20cm

6.4

25cm

3.7

30cm

1.9

image00.png

As you can see from these results as the light intensity increases, the resistance decreases. I need to find the range of light levels the LDR can detect and distinguish how sensitive it actually is. The maximum resistance  it is possible to get from the LDR is 550kΩ. This is when there is maximum light shining on the LDR. The minimum resistance that is possible is 0.90kΩ. This is when the LDR is submitted to complete darkness.

...read more.

Middle

The two LDRs are going to be separated by a sheet of card straight down the middle of the card that the LDRs are mounted on. This is so the light falls on one or the other of the LDRs. It will cast a shadow so one of the LDRs will be in perfect light and the other will be in near darkness. As the light nears the middle, the light will fall equally on both. By doing this I am emphasizing the amount of light on the LDRs, creating a bigger difference and more emphasized results.  I am taking the results of the voltage of one of the LDRs. If I took the voltage of both of them, it would always read 12v. The lamp that I am going to use is 12v, 90watt bulb and it is going to be placed 15cm away from the LDRs and it will be moving from right to left at 5cm intervals in front

...read more.

Conclusion

 Another reason for the irregularity of the results could be to do with the section of card that was placed between the two LDRs. This could have cast a shadow on one of the LDRs while the other was in full light causing the difference and unpredictable nature of the results. As the light moved closer to the middle, the shadow would have got shorter and then disappeared when it hit the middle (40cm). This is apparent by the way that at 40cm all of the reading are the same. When the LDRs are only 5cm away from each other, the shadow will cover it more and for longer, producing the more dramatic set of results.

Because the piece of card stayed the same and didn’t change, when the LDRs are further away from each other, the shadow doesn’t affect the results as it would the other two sets. This could explain why the results for the 25cm result seems inverse to the others, the shadow isn’t reaching the LDRs now because they are further away from each other.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

or


Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. Using an LDR to detect the intensity of plane polarised light allowed through a ...

    Detector Now that I have considered my choice of emitter, I think it is necessary to discuss why I chosen my particular sensor. There were four different components I had the chance of using. The advantages and disadvantages of all four are contained in the table overleaf.

  2. Sensors cwk. The aim of this coursework is to construct a potential divider circuit ...

    can't tap the voltage off at any point therefore we use two resistors instead. The voltage is then measured between the two resistors. The diagram below illustrates this: V1 is the voltage in and V2 is the voltage out. If we know V1, R1 and R2 we can use the

  1. Physics - Resistivity

    is a potential difference or p.d. You can add two voltages in a circuit together, using Kirchhoff's circuit laws. CURRENT Electric current is a net flow of charged particles, usually around a circuit. The direction of flow in circuits can change depending on whether you are using 'conventional current' or the actual current flow.

  2. Choosing a light source

    The filament within the halogen bulb does not burn out as quickly, increasing the life of the bulb itself and also the bulb can be run at much hotter temperatures, producing more light per unit of energy. Disadvantages: Low voltage halogen lamps are most suitable for highlighting features such as

  1. The aim of my investigation is to investigate how the brightness (intensity) of light ...

    As there will be 5 readings, there will be 5 different distances. 0cm will not be one of the distances because the LDR can't be put in to the Bulb. We will keep small distances because of the external light entering from the windows of the classroom.

  2. To Investigate How the Resistance of the Light Dependent Resistor Depends On the Current ...

    And the voltage in the circuit is equal toV2 plus the voltage of R2. The Voltage in the circuit keeps the same and the voltage of R2 increases, so V2 decreases. 2. I predict that the graph of the resistance of the LDR against to the current of the light

  1. Resistor - What do resistors do?

    For the resistor shown below, the first band is yellow, so the first digit is 4: The second band gives the SECOND DIGIT. This is a violet band, making the second digit 7. The third band is called the MULTIPLIER and is not interpreted in quite the same way.

  2. Designed to familiarise the author with the science national curriculum and in particular the ...

    The latter part reports upon the demands of the syllabus for the chosen topic area, with regard to knowledge, understanding and process skills. 2.1. Text Book Review Howe, L., 1997, Making It Work, Collins Educational, London. (KS 1 & 2)

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work