We decided to use a magnet because it is probably the best material available to use for a core and was really the only material available apart from steel. Materials that could also be used as cores include Steel, but these become permanent and are therefore useless in an electromagnet.
According to the book, 'The Working World of Physics', Alnico and Ticonal, which are alloys of iron, nickel, aluminium and cobalt, could also be used but we did not use them for two reasons:
They were not available. They become permanent magnets so are therefore useless to use more than once without demagnetising them.
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Jack Mariner Physics Coursework
Hypothesis
I predict that as the amount of coils increases so will the magnetic fields surrounding the electromagnet. Therefore, I predict that the amount of clips picked up will increase as the number of coils increases until eventually the electromagnet can't pick up any more pins (the point of magnetic saturation).
Equipment
- Mat (to protect the surface of the bench)
- Magnet (part of the electromagnet)
- Wire (forms part of the electromagnet and is what we are testing)
- Power Pack (to input the current)
- Crocodile Clips (to take the electricity to the Electromagnet)
- Paperclips (to experiment with)
- Electrical Scales (for weighing the paperclips)
The apparatus will be set up as follows:
Safety Precautions
Although this experiment is very simple, safety must always be taken into account. Firstly, electricity is being supplied so all components should be handled carefully. Avoid contact with water. The only other safety issue that needs to be taken into account when undergoing such an experiment is that magnets can ruin electrical devices such as watches etc, so it would be advised to prevent contact between such objects.
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Jack Mariner Physics Coursework
Suitable Range
The range of the number of coils that I shall be experimenting with is from 10 to 20 coils. I shall take 12 readings. These will be with 10 coils, 12 coils, 14 coils, 16 coils, 18 coils and 20 coils. In order to produce accurate results, more than one reading must be taken. This is why I have taken two readings. These will then be averaged. The reason for choosing these particular amounts is because they are spaced out evenly and easy to compare.
Method
The first thing to do is to get our equipment out and set it up. Then get the electromagnet ready. To do this you coil the wire around the magnet. This should be done so that the number of coils is what you are testing i.e. I will start off with 10 coils then 12, 14, etc. You should do this, leaving the two ends of the wire free for crocodile clips. You then attach the crocodile clips to the ends of the wire connecting them to the power box. Turn on the power to the required voltage (I used 8v) and then bring the magnet towards the paperclips. Now, the paperclips should be attracted to the magnet and should stick to it. Turn the power off gathering all the attracted clips and then weigh this amount.
This experiment was a fair test because:
- Electrical scales where used. These are usually extremely accurate, ensuring a fair test.
- The same power pack was used each time.
- The same paperclips were used each time and the clips were all roughly the same weight.
- Only one factor (i.e. the amount of coils) was changed.
- The core of the electromagnet always had the same surface area.
- The same equipment was used each time.
- The clips were all made of the same material.
Key Factors, which could affect this experiment, were:
- The metal that the core is made of.
- The accuracy of the amount of coils being used.
- If the clips are magnetised.
- If the core stays a permanent magnet after the electricity is turned off.
- If all the clips were made of the same metal.
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Jack Mariner Physics Coursework
It was necessary to repeat each result twice to confirm that each result was correct and not anomalous.
Results
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Jack Mariner Physics Coursework
Analysing the results
The first thing that is evidently wrong with my results is the fact that there is an occurrence of anomalous results. It is visibly clear that the results when having twelve coils are incorrect. Either this or all the other results are anomalous and this is fine.
Other observations from the results are the fact that throughout the readings, the first and second readings all have completely varying relationships. For instance, testing with 14, and 16 coils. The first and second readings for both of these are extremely similar, whereas the readings for 10 coils, varies immensely. Nonetheless the averages all seem to follow the line of best fit, with the exception of anomalous results.
Conclusion
The results did show that my predictions had been right. The amount of paperclips increased with the increasing number of coils.
Evaluation
I consider this experiment to be a success. The plan was followed very well and the results were of good quality. The measurements were done accurately, and a fair test was achieved. The procedure used was also a very fair and efficient one.
Although the experiment was a success, I am still bothered by the fact that anomalous results occured in my experiment. I think that the reasons for these results were because of time limitations. We had very little time to accomplish this task successfully, so mistakes were inevitable.
The improvements that could be made in doing this experiment are:
- To have more time to do the experiment so that it isn’t done making careless mistakes and if mistakes were made, there would be enough time to redo what was needed.
- Using Iron filings or something that would give a more accurate weight.
- Taking more readings. These would give much more accurate results. Two readings are never enough but in the time I had this had to be done.
