The other variable is the current (controlling the amount of electricity which passes through the circuit.) The prediction is that when the current is increased the electromagnet will be stronger and when it is decreased it will be weaker. This hypothesis comes from the same logic as what happens when the amount of coils is altered. If more current is flowing through the circuit it will increase the size of the magnetic field or the amount of concentration of electricity, when the current passes through the coils; therefore increasing the amount of domains in the core which become aligned and increasing the strength of the magnet, so that it pick up more paperclips.
Plan
You will need: 1 power pack, 1 ammeter, 2-3 leads with crocodile clips, 1 iron nail, 1 wire, a collection of paperclips and access to an AC power supply.
- Plug in the power pack to the AC power supply and connect the leads with crocodile clips.
- Take the iron nail (core) and wrap the wire around it to make the coils, connect it with crocodile clips to the leads therefore completing the circuit.
- Connect the ammeter to the circuit and set it to the setting where there is a white dot to measure the current in amps.
- Test that the electromagnet works by turning the power pack on and seeing if it attracts the paperclips.
- Change the variable you have chosen e.g. the current (increase and decrease) by turning the central dial on the power pack. Change it by increasing the power one amp at a time and don’t exceed 5 amps because it can damage the power pack.
- Measure the current with the ammeter taking the measurements in amps.
- You may decide to change the other variable - the coils (more and less) and measure the amount by counting them.
- Each time you change a variable test the electromagnet by how many paperclips it attracts and record your results on paper.
Tip: Before putting the iron core into the circuit bang it on a hard surface so that the all the domains become misaligned again. Do this because the cores sometimes hold their magnetic charges from past experiments and can affect accuracy of results.
Method
The plan was followed all most exactly and the variable selected was to change the current. The experiment was improved by adding a variable resistor to the circuit; this enabled us to control the current passing through the circuit more accurately than on the power pack because the current could be altered to very exact decimal places. It made the experiment more exact because the current (amps) could be record to such minute quantities and it was much easier to get exact figures of amps when read off the ammeter. It is not shown on the diagram below but actually in the experiment an iron nail which acted as a core for the coils to be wrapped around was used. Using a core improves the experiment because it is able to concentrate the magnetic field and all the domains inside it are aligned so there is a solid magnet that paperclips will be attracted to, instead of just lots of coils. The core holds the magnetic charge from the coils, magnetising it which is essential for our experiment to attract the paperclips.
Diagram
Results Table
Graphs
- The graphs have been drawn separately on graph paper using the average results column as the points to plot, from the results table.
Analysis
The graph suggests that as the current increased the number of paperclips which were picked up also increased thus indicating an increase in the strength of the electromagnet. This supports the prediction and happens because when the current is increased there is a greater concentration of electricity passing through the coils causing a stronger magnetic field; to which the magnetism gets concentrated in to the core. Thus, causing the microscopic domains in the core to align with clear north and south poles and the core to become a magnet and attract the paperclips. So, if the current is lowered then so will the magnetic field be weaker and the fewer domains aligned hence a weaker magnet, hence less paperclips picked up. The same goes for increasing the current e.g. stronger magnetic field, more domains aligned, stronger magnet, more paperclips attracted etc.
On the graph three lines of best fit have been drawn to show different trends in the results each helps to prove the prediction by roughly following the trend which states: the larger the current the more paperclips picked up. There could also be an alternative conclusion to line number three because we can see that from the start it continues in quite a steep upward gradient but then curves more and levels out until it is almost continuing horizontal. This line suggests that the current has increased as predicted up until that point at which the total number of paperclips that can be picked up has been reached so the graph won’t continue to increase but just go steadily horizontal. This may be because all of the domains inside the core have been aligned once the current reaches a certain number of amps meaning that the strength of the magnet can no longer increase so it will never exceed the number of paperclips that it picks up there. The magnet is at its strongest so the number of paperclips picked up will not increase after that point. Another possible explanation is that no more paperclips could physically fit onto the end of the magnet so once all the room is taken up no more paperclips will fit on even if the magnet was strong enough to attract more, hence the graph also continuing steadily horizontal.
Other possible odd results could be due to the fact that the cores can sometimes hold their charges from previous experiments so they have got more magnetism than you think, however this should have been avoided because the nail was banged on the desk before the experiment to misalign the domains again as it said in the plan.
Evaluation
The test went reasonably well evident by the fact that the graphs showed good lines of best fit and that the results helped to prove the prediction. The experiment in itself was not really a very reliable one as paperclips are awkward shapes and sizes not really best suited to measuring strength, the experiment might be improved if a different form of measuring was found such as smaller pieces of metal maybe with all the same mass like tiny 5g weights or even measured amounts of iron fillings (that test might also prove difficult as iron fillings are very difficult to get off the magnet.) It might even help to just get paperclips of the same mass and size to keep the amounts fair, or even do the experiment with different size paperclips each time such as small, medium, large. Further work could be done to improve the experiment such as repeating the results maybe a greater many of times to come to a more accurate average or carry on the experiment with a higher current to see which results from the lines of best fit most fit the trend.
The problem with their being not enough space on the nail could also be solved by using a bigger nail and it could also check the theory of all the domains being aligned in the other size nail because it would give a greater range of results and allow the graph to be continued to check what line best fits the trend – this would very much help to pin point an exact conclusion. The same problem of there being not enough space could also be solved by designating a certain amount of space to be tested say 1 inch at the end of the nail and maybe varying that amount. The actual paperclips could be arranged differently as the strength of the magnet could be tested by adding each paperclip on in a chain so the magnetism goes into each one – this experiment could rapidly change the results as the present only tested how many paperclips would attract all touching the nail. Finally, the metal by which the core is made from could also alter the results by how magnetic the metal is, so it could be another experiment to see the strength of the magnet with different cores of different magnetism, such as iron, copper and zinc etc.
