• 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. The factors affecting the current flow through a conductor at a constant temperature.

    My hypothesis was nearly correct except that I was mistaken about the direction of results in proportion to resistance. I thought that the current and voltage would decrease as the resistance increases. It was the other way around, they both increased, proportionally.

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

    Average Resistance (?) 10.0 4.72 20.0 9.09 30.0 13.96 40.0 17.20 50.0 24.30 60.0 29.52 70.0 31.88 80.0 40.16 90.0 44.59 I calculated the cross-sectional area of the constantan wire which I used by firstly measuring its diameter using the micrometer mentioned before and then by using the formula below: Cross-sectional area of wire = ?d2/4 So: Cross-sectional area of wire = ?

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

    Phototransistor * Phototransistors are able to amplify the changes that occur * Can be photovoltaic or photoconductive, giving greater flexibility * More sensitive due to the two PN junctions. * The 'extra functions' that the transistor has cause it greater fragility and cost; for functions I will not need in my coursework.

  2. To investigate whether the two resistors and the bulb given is an ohmic or ...

    air conditioners and don't turn them back on during the experiment, shut all windows and curtains to prevent sunlight heating up the room, perform the experiment in a smaller room so that the temperature can be more easily monitored. In addition, a thermometer can also be used to record the temperature in the experimental area.

  1. Relationship between the current and voltage.

    The current readings were accounted in amps, when they should have been measured in Millie-amps, which would have given even more accurate results. From fig 2, which was the results for the 2-Ohm resistor, it is evident, that like the 1-ohm resistor, there is a directly proportional relationship between pd.

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

    Results & Calculations Number of blocks 2 3 4 Pile up Side by side Pile up Side by side Pile up Side by side Applied force F (Kinetic friction fk) 2.6 2.6 3.2 3.8 4.6 5.2 Normal force R (Weight of the blocks)

  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. 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