Physics Assignment Flashcards
To learn my points for the physics assignment write up. (22 cards)
Title
How changing the distance of a light source affects the resistance of an LDR.
Aim
To investigate the relationship between changing the distance of a light source from an LDR and the LDr’s resistance.
1) Underlying Physics - What is an LDR
- light dependent resistor
- as light intensity increases the resistance decreases
- has the greatest resistance when in darkness and vice versa.
2) Underlying Physics - How does LURD relate to the experiment
As the distance between the LDR and the lamp increases, less light reaches the LDR.
Therefore, the resistance of the LDR increases with greater distance from the lamp.
3) Underlying Physics - Non linear relationship between resistance and light intensity
The relationship between resistance and light intensity is non-linear.
A small change in light intensity can lead to a larger change in resistance.
This suggests that my graph will be curved.
4) Underlying Physics - Photoconductivity
LDRs operate using photoconductivity, where light photons increase the conductivity of the semiconductor, decreasing resistance.
Increased conductivity allows charges to flow more easily, lowering resistance.
5) Underlying Physics - Non Ohmic Conductor
LDRs are non-ohmic conductors, meaning their resistance does not follow Ohm’s law.
A non-ohmic graph would be created when plotting voltage against current for LDRs.
6) Underlying Physics - What are LDRs affected by?
Can be affected by the environment
LDR resistance can vary significantly with temperature.
Very bright light can cause a permanent decrease in resistance or damage the semiconductor material.
Method (3 stages)
Measurement Tool: An Ohm meter was used to measure the resistance of the LDR (Light Dependent Resistor).
Variable Manipulation: The resistance was changed by placing a lamp at different distances from the LDR.
Data Collection:
The resistance and the distance from the LDR was measured each time the lamp was moved.
This process was repeated multiple times to ensure reliable results.
1) Analysis - Overall
Comparison of Graphs: Both the internet graph and my graph showed fairly similar results.
2) Analysis - Key Comparison
Key Comparison: The relationship between the distance from the lamp and the LDR’s resistance in both graphs is not directly proportional
3) Analysis - Similarities
Graph Analysis:
Both graphs have a trendline that is a curve.
My graph’s trendline equation does not follow the straight line equation (y = mx + c).
4) Analysis - Differences
Data Points Used:
My graph used 9 data points, while the internet graph used 7 data points.
Using 9 data points provides a clearer view of the trend and reduces outlier errors.
1) Conclusion - in conclusion
Conclusion: As the distance from the lamp increases, the resistance of the LDR (Light Dependent Resistor) also increases.
2) Conclusion - Key finding
Key Finding: The relationship between distance and resistance is not directly proportional.
3) Conclusion - Graph analysis
Graph Analysis: The graph did not follow a straight line equation, indicating a non-linear relationship.
4) Conclusion - link to aim
Link to Aim: The discovered relationship shows that while the values are positively correlated, they are not directly proportional, as evidenced by the curve in the graph.
1) Evaluation - Source of uncertainty
Source of Uncertainty:
The main source of uncertainty in the experiment was heat from the hot filament lamp affecting the resistance of the LDR.
2) Evaluation - impact of heat on LDR
Impact of Heat:
Increases in temperature can decrease the resistance of the LDR, even without light present.
This effect needed to be monitored during the experiment.
Can also damage the LDr is exposed to excess heat for too long
3) Evaluation - how to mitigate uncertainty
Mitigation Strategy:
To combat heat effects, two panes of glass can be used, separated by a layer of air to act as an insulator.
4) Evaluation - mitigation limitation and solution
Limitations of the Mitigation:
Some light may be lost when passing through the glass.
This limitation can be addressed by adjusting the results to account for the reliable loss of light.
5) Evaluation - benefit of mitigation (overall)
Overall Benefit:
These adjustments make the experiment more accurate and reliable by reducing potential errors due to temperature.
It also prevents long-term damage to the LDR from excess heat.
