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# Physics Lab Report. Aim: To find out how a light dependent resistor is affected by light intensity.

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Introduction

What is the relationship between light intensity and resistance in a Light Dependent Resistor?

Aim: To find out how a light dependent resistor is affected by light intensity.

Hypothesis: A light dependent resistor is one that changes its resistance with a change in the light intensity on it. Hence if we can find the light intensity that is on the resistor and its resistance, we can see what factor the resistance is affected by.

Variables:

Independent: Light Intensity

Dependent: Current

Controlled: Voltage, Resistor used, Ambient light, Filament Light Bulb used, light sensor and resistor.

Apparatus:

1. Filament Light Bulb

2. Clamp Stand

3. Light Dependent Resistor

4. Voltmeter

5. Wires

6. Light Sensor

7. Logger Pro

8. Laptop

9. Power Supply

Method:

1. Connect up all the wires in order to the resistor and the power supply.

Middle

0.012

0.013

0.013

0.013

0.012

6318

7623

0.015

0.016

0.015

0.015

0.018

Data Processing:

First we calculate the average current and average light intesity

 Average Light Intensity (Lux) Average Current (± 0.001A) 1290.00 0.0060 1803.50 0.0072 2154.50 0.0078 3474.00 0.0102 4531.00 0.0126 6970.50 0.0158

Using V=IR we can calculate resistance since voltage was set at 1.2V at the beginning of the trials. We get the following values:

 Average Light Intensity Resistance (ohms) 1290 200.00 1803.5 166.67 2154.5 153.85 3474 117.65 4531 95.24 6970.5 75.95

Conclusion

1. The light sensor gave a band of values in which the intensity could be. It did not give one specific value.
2. The resistance voltage was given only to one decimal place.

The assumptions in the experiment were:

1. The light in the room did not change in intensity.
2. The light sensor and the resistor were the same distance away from the filament bulb.
3. There was no resistance in the wires.

The improvements that could have been made were:

1. A better light sensor could have been used.
2. We could have made sure that the light sensor was exactly the same distance away from the bulb as the resistance.
3. The room could have been made darker
4. The experiment could have been carried out further away from other students to prevent the light from their experiment interfering with mine.

This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.

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