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

To Investigate How the Resistance of the Light Dependent Resistor Depends On the Current In the Light Bulb?

Extracts from this document...

Introduction

TO INVESTIGATE HOW THE RESISTANCE OF THE LIGHT DEPENDENT RESISTOR DEPENDS ON THE CURRENT IN THE LIGHT BULB?

PANNING:

Aim:

In the experiment, I am going to investigate how the current in the light bulb affects the resistance of the Light Dependent Resistor (LDR).

In this experiment, I am going to vary the resistance in the light bulb circuit in order to vary the current in the light bulb. At the same time, I am going to find out how the resistance of the LDR is affected by the brightness of the light bulb.

In the following stages, I will need this scientific knowledge:

The current in a series circuit is the same everywhere, but in a parallel circuit, the sum of the current in the branches is equal to the current of whole circuit.

The voltage in a parallel circuit is the same everywhere, but in a series circuit, the voltage of each component added together is equal to voltage of the supply.

Prediction:

I predict that:

  1. When the light bulb becomes brighter, the resistance of the LDR decreases.

This is because the Light Dependent Resistor (LDR) is made of Cadmium Sulphide. This semiconductor (a very poor electrical conductor) has a very high resistance in the dark, but when light is shone on it, its resistance falls. This means that when the light bulb is bright, the resistance of the LDR is low. Otherwise, the resistance of the LDR is high.

When the resistance of the variable resistor R1 decrease in circuit 1, the reading I1 will increase.

...read more.

Middle


The circuit was set up as shown above. A table was drawn out and the results were recorded.

To improve the accuracy, compared to my preliminary results for my main
Experiment, I have decided to use a 20MA ammeter in the 1
st circuit and use a 200MA ammeter in the 2nd circuit.

To collect the data for my graph I have chosen to take a range 2.5MA of the current of the light bulb. I have chosen a range of 20 as plot an accurate graph; I will need at about 20 points to mark on the graph if I want to make precise and reliable results, to see if there are any patterns and trends.

...read more.

Conclusion

One of the difficulties in this experiment is to control the current of the light bulb, when I carried the variable resistor R1, the current of the light bulb changed rapidly, so it is hardly to control it exactly what I want.

During my experiment, I have noticed several mortifications I could make to improve on the Investigation if I was to repeat it. 
The first of these modifications would be I could use a new or higher quality digital voltmeter and ammeter.

The graph shows that my results are reliable as there are only two anomalous points, to improve the reliability of my results, I could also have repeated the same lengths of wire more times.

As well as making these modifications, I could also expand on my investigation by measure the voltage of the light bulb in order to find out the power of the light bulb.

This is because the brightness of the light bulb is depended on the power of the light, in order to find out he power of the light bulb, I will need to know the voltage of the light bulb and then use power=current* voltage to find out eh power.

I will use the circuit and method used, as it was quite suitable although I would make the modifications above to improve my results. If I did this experiment again I would defiantly use top quality equipment, I would control the entire confounding variable, which includes the brightness of the room.

My alternative conclusion is that: the resistance of the LDR decreases as the current of the lamb decreases.

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

    * Slower response times, but this is negligible due to there being no sudden changes Photodiode * Can be photovoltaic or photoconductive, giving greater flexibility * React negligibly to ambient light * Can be used with many different frequencies of light based on material of the window * Very fast

  2. Investigating the effect of 'length' on the resistance of a wire

    For 90cm length: 43.33+45.84= 89.17�2= 44.585 rounded up to 2 d.p--> 44.59? The third set is the average of the two sets of resistance calculations above. The results are shown below: TABLE No3 Length of Wire (cm) Average Resistance (?)

  1. To investigate how the temperature affects the resistance of a thermistor.

    temperature of a thermistor and the resistance across it I can conclude that my prediction was correct. A thermistor is a semi-conductor and so this means that as the temperature across it and the amount of energy being transferred into the electrons increases the resistance decreases.

  2. The aim of the experiment is to verify the maximum power theorem and investigate ...

    in horizontal position as much as possible, we also can measure the degree of the direction of the applied force to the horizontal by using the projector. Besides, the roughness of the sand paper is not the same over the whole sand paper.

  1. 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.

  2. resistivity if a nichrome wire

    To overcome this problem the rust can be cleaned with sandpaper, or even replaced by new ones. Thickness of wire This may differ on the wire, as the wire may not be uniformly thick. This causes a change in the cross sectional area of the wire.

  1. Free essay

    The Relationship Between the Input and Output of an LDR

    Strategy I am expecting the potential difference to increase the further away the bulb is moved from the LDR. The light falling on the brown 'zigzag' lines on the sensor (cadmium sulphide cells), causes the resistance of the device to fall.

  2. Geothermal energy is not easily accessible with our current technology. Our main focus was ...

    If the nuclear product gets released into the atmosphere, nuclear fallout would occur and that has a lot of hazardous effects. Another dangerous effect of the explosion is a possible trigger of a fault rupture which would cause a high magnitude earthquake.

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