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Investigating Electromagnets

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Physics coursework Investigating electromagnets Aim: To investigate a variable that affects the strength and effectiveness of an electromagnet. Introduction: In my following coursework, I will carry out an investigation on a variable, which affects the strength of an electromagnet. I tend to also create an accurate enough analysis, which will help me determine why the variable investigated, affected the strength of the electromagnet. Background research: An electromagnet is also known as a solenoid. An electromagnet usually consists of coils of wire wrapped around a magnetic core. The core could be Iron, nickel or cobalt, which are good electromagnets. Usually an electromagnet would consist of an iron core as this is the best at magnetising and proves readily available, because of these reasons I think the core, which I will use for the investigation would have to be an iron based core. Other cores that could be used prove ineffective as they become permanently magnetised so therefore are unuseful as they can only be used once. Above we can see the magnetic field generated by a round wire carrying electricity (picture taken from encarta). This shows the way in which an electromagnet works. If a solenoid is wound in the form of a helix, there will be a magnetic field. However, with the introduction of an iron core to go within the helix the strength of the field will be greatly increased. Microscopic domains in the core align themselves in the direction of the field thus increasing the strength of the field. When all the domains have aligned the core would have reached its saturation point. Iron cores tend to have domains which are more jumbled up so when they are objected to a magnetic field or solenoid their domains become lined up but when the outside influence is removed the domains become jumbled up again. Variables that affect the strength of an electromagnet: Sources: physics matters (GCSE textbook), A-level textbooks, Microsoft Encarta 1999 and set knowledge Current: As the current is increased in a wire, the strength of the magnetic field becomes greater and therefore more effective. ...read more.


Proposed results table The extension measures the strength of the electromagnetic field. Number of coils Extension 1 Extension2 Extension 3 Average extension 10 20 30 40 50 60 70 80 90 100 Observation In my experiment, I had an ammeter placed in the circuit to see how current may relate to the results, which I obtained. The different currents are displayed in the extra column that I decided to add on to my original proposed result table to show current. I had observed that in the experiment that current had increased and decreased at several points following no pattern. When there were more coils on the nail the extension did tend to increase but in a few occasions, it did stop extending the Newton meter at short distances. These anomalous results may have been the result of the holder of the Newton meter holding the Newton meter in a certain way not allowing getting near optimal results. This may have been because as the Newton meter was moved the surface area contact between the hook and the iron nail might have been decreased. So the electromagnetic influence of the nail on the hook could have been decreased, also if the Newton meter was pulled really quickly then the full extension achievable may not have happened due to the rapid movement. When there were a greater number of turns on the electromagnet, I observed that the electromagnet would become quite hot and subsequently the power pack would reset, this meant we had to take our results as quickly as possible before the power pack would reset. As far as I could tell, there was no residual magnetism on the electromagnet. Actual results table The table below has units for extension (strength of field) measured in Newton meters in columns 2,3,4and five. The current is measured in amperes. All the below results are for a voltage of two. ...read more.


All my results fitted the pattern in my graph to an extent that I could say that all my results were justified and accurate. I would carry out an experiment on the nail when there were no coils wrapped around it to see if the nail starts with residual magnetism so can be taken into account in my analysis. If I had more time to carry out experiment, I would have investigated a greater number of coils to see what the further affect would have been. In addition, with time permitting I would have carried out a greater number of repetitions. I feel quite surely that the results that I got were accurate enough for me to form an accurate conclusion. My averages show this as they all follow a general trend that is stated in my analysis. However, there are a few anomalous results e.g. column extension 2, number of turns, 90 where the extension in fact decreases from 3 Newton meters to 2.9. These results could be down to several factors such as the inaccuracy of equipment or human error, but these results only slightly affect the average so the conclusion remains valid. I also would have used a method in which I could hold the Newton meter in the same place and slowly lift it at a constant rate; this could have been done with a robotic arm. In addition, I would have used a very accurate Newton meter with an easier to read digital display. Another method would be to have used an electronic scale and see by how much a magnet affixed to the scale would be attracted to an electromagnet hanging over it, with increasing number of turns around the core. The negative readings on the scale could be used to see by how much the nail attracts itself to the electromagnet. This method would require a very sensitive scale (0.001g) because the nail will be very minutely attracted away from the scale. ...read more.

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