• 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

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. Physics - Resistivity

    0.1 2 3.17 3.03 2.94 3.05 0.12 1 2.5 1.96 1.92 2.13 0.32 0 0 0 0 0 0 I decided that because I excluded my anomalous first repeat, my standard deviation was very small, so drawing error bars onto a graph would be useless.

  2. Investigating the factors affecting the size of current flowing through a length of resistivity ...

    I calculated that doubling the length of putty increased the inverse current by a factor of 1.968. I concluded that within the limits of experimental error this value could be considered to be about 2. This meant that doubling the length of putty halved the amount of current flowing through it.

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

    For example, there is still the problem of needing holes for the LDR and also the fact that the small shade will shade the light entering the LDR. It also doesn't stop the problem of creating a shadow when trying to read the voltmeter, if I try to lean over it.

  2. A2 Viscosity investigation

    As the temperature was probably lower than that stated I feel that the viscosities are probably lower than theses stated. The inaccuracies and how they could have affected the results are discussed below. Limitations and factors affecting the investigation: Various things will have affected this investigation and increased the errors and reduced the accuracy.

  1. Light intensity

    Some small errors could creep in when reading off the Multimeter. The resistance readings will start to fluctuate slightly. I will take the best reading I can by waiting until the Multimeter stays on one number. The more accurately I set the Multimeter, the harder this is to do.

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

    of a high resistance superconductive materials such as cadmium sulphide (CdS), which conducts better when light shines on them. To get a large change in resistance, the resistance is increased by laying down the CdS in a long zig-zag strip. The change in resistance be detected using a potential divider.

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

    As the voltage stays the same here, so the current, which is equal voltage divide by the resistance increases as well. The reason why V2 decreases is that when the current in the circuit increases, the voltage of R2 increases as V=IR and R keep the same.

  2. Resistor - What do resistors do?

    Some types of wirewound resistors can pass large currents wihtout overheating and are used in power supplies and other high current circuits. Colour code How can the value of a resistor be worked out from the colours of the bands?

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