Introduction: During the past few years there have been a sharp rise in fire incidents all over Qatar. This poses a great concern to general safety in Qatar. According to the QSA in 2011 there have been a total of 1026 fire incidents. The majority of these incidents have been caused by electrical problems. For that reason I will conduct a lab report to investigate electrical safety.
Electrical problems cause fires when a high current runs through the circuit. When a high current runs through a wire it will heat up, to much heat will cause a fire. By investigating how adding more electrical devices (eg. electric bulbs) to a circuit affects the current, I will be able to determine wether the number of electrical devices connected to a single plug will affect electrical safety or not.
Aim: I will investigate the relationship between the number of bulbs in the circuit and the current going through it. I will do this by making a parallel circuit with an ammeter and one light bulb, I will then measure how the current changes every time I add a light bulb.
Independent: Number of light bulbs connected to the circuit
Dependent: Current going through the circuit
Control: Power supply, room temperature, bulb size, all bulbs connected in parallel, connecting wire thickness, material of connecting wire,
Hypothesis: I think that as the number of light bulbs increases so will the current. This is because when there are more light bulbs in a parallel circuit there is less resistance. There is less resistance because the electricity can pass through more branches (resistance). When there is less resistance there will be a higher current. This is dictated by the formula I=V/R (current = voltage divided by resistance).
-5 light bulbs
-11 connecting wires
-10 ‘crocodile’ clips
Diagram: Refer to attachment on hard copy
1. Set up apparatus as shown in diagram.
2. Measure current, and voltage
3. Add light bulb, and measure current and voltage
4. Repeat step No. 4 three more times
5. Return apparatus and process data
Number of Bulbs Current (Amps) Voltage (Volts) Power (V*I) (Watts)
1 0.2 1.0 0.3
2 0.3 1.8 0.6
3 0.5 1.8 0.8
4 0.6 1.7 1.1
5 0.8 1.7 1.4
Graph: Refer to attachment on hard copy
Conclusion: In my hypothesis I predicted that as the number of light bulbs increases so will the current. Looking at my results I can confidently say that this hypothesis was correct. The results clearly show that the current increases proportionally to the number of light bulbs.
There is no unusual data, and there are no outliers in the data. This shows that there is a clear trend in the data. The data is closely correlated as all the points lie close to the best fit line. The clarity and correlation of the data shows us that my hypothesis was correct and that the current is proportional to the number of lightbulbs.
The data that I have gathered from this experiment is very valuable when investigating electrical safety. This simple experiment performed in a lab under controlled variables relates directly to people using electrical devices at home. If various electrical devices are connected to a single plug, it will become hot and cause a fire.
Evaluation: In this experiment there were some changes of the method which I could have made to improve the reliability of the data. The most important change would be to increase the amount of trials, then take the average. The challenge with doing this would be that it would be very cumbersome to set up three different circuits and take results from each separately and it would be very time consuming.
When making this experiment I made sure to use electricity with no higher voltage than 2V, this means that I could not be electrified when conducting the experiment. Looking back at my method I think that it would be important to include this not so that any student performing a lab report like mine will be able to conduct the experiment safely.
Looking at the data I collected there seems to be an abnormality in the voltage. Although I did not change the voltage from the power supply, the data from the voltmeter shows that the voltage was not stable throughout the experiment. This could negatively affect the experiment because it means that one of the variables which should be the same is changing. The cause of this change in voltage could be fault in the equipment. If this experiment were to be conducted again, I should check for abnormalities then review what malfunction is causing this abnormality.
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