One of the reasons that I know that there is a magnetic field around a wire when electricity runs through it, is because* Christian Oersted discovered it in 1819*.
I think, that the reason why the iron core gets magnetised is because inside it are lots of pairs of electrical charges or magnetic poles, *of equal magnitude*, separated by a small distance. These electrical charges are called dipoles. So when the iron core becomes magnetised, it’s because all the dipoles have turned round so they are all the facing the same opposite pole.
So, if I increase the voltage it will increase the amount of dipoles turning to face the same direction, making the electromagnet stronger. The larger the amount of voltage, the faster and more dipoles turn, obviously making the electromagnet stronger as it is increasing the magnet field around the iron core.
I increase voltage instead of current, as in a lab. you can’t increase current as it is highly hazardous. So instead I increased the voltage as it is directly proportional.
Plan ~ here is what I am going to do
First I shall set up my apparatus as shown in the diagram, and then I shall:
2. make sure everything is a fair test by using all the same equipment.
3. I will make sure that the wires are of the same length
4. Then I shall make sure that the wire that is to be wrapped around the iron core has 3cms of plastic coating insulation taken off at both ends of the wire.
5. I will then wrap the wire in 15 coils around the nail and connect 1 of the wires to the positive (+) terminal and connect the other wire to the negative (-) terminal of the battery pack.
6. I will then place paperclips on the end of the iron core after turning on the battery pack and increasing the current.
7. While increasing the voltage I will place paperclips onto the end of the core until one falls off.
8. The amount of paperclips that are stuck onto the core will be the results that I will record in a table then I will make a graph to show them.
9. I will repeat my experiment three times to make sure that I have accurate readings.
Results ~
What I changed: Voltage
Conclusion ~ what I have found out by looking at my graph and what I think is happening:
From look at my graph, you can see, when I increase the voltage the electromagnet becomes stronger as it holds more paperclips. You can see this in the graph.
The graph supports my prediction as I predicted the shape of the graph. If I carried on the experiment for a longer period of time and had a bigger range you would see the line straighten off. That would be because all the dipoles have turned round and would be facing the same direction. There isn’t any direct trends on the graph, just as the voltage is increased the electromagnet holds more paperclips (becomes stronger). At 3, 4 and 5 volts, the electromagnet increases its strength by one paperclip. Then the trend breaks and there is no pattern in which the strength increases. At 9 volts there is an anomalous reading ~ which I have ignored for my “line of best fit”. The anomalous reading, I feel, has not affected the results as a whole.
Evaluation ~ How well the experiment went:
My results were not entirely accurate as when I repeated the experiment three times I didn’t always get the same results. I got an anomalous reading at volt 9 as it decreased in strength from 13 paperclips at 8 volts to 12 paperclips; it then went to 14 paperclips at 10 volts. I ignored the anomalous reading when drawing a “line of best fit”. The evidence from my results was accurate enough to support my prediction and showed the evidence on the graph produced.
The procedure I used was good enough to get results to support my prediction, yet I do feel that they could have been more accurate with a different procedure.
Accuracy ~ How accurate were your results and why are they not perfect?
My results weren’t perfect as I didn’t get the same results 3 times when I repeated the experiment. My accuracy could have been improved by using a volt metre so I could see the precision of the amount of voltage as the battery packs are old and unreliable. I also got an anomalous reading at 9 volts, were the electromagnet’s strength decreases from 13 paperclips to 12. This maybe because the battery packs are old, or simply because of human error.
Improvements:
To ensure that I have accurate readings if I do the experiment again, I would use a volt metre so I can see the precision of how many volts I am using. I would also have a 1 minute gap between each reading as resistance builds up in the wires if there isn’t a break, therefore making the results less accurate. I would do the experiment over a bigger range as you would see the full accuracy and results from the experiment. I would tap the iron core on the table making it lose all its magnetism before a reading. In addition to that I would make sure all the equipment was new.
