Electromagnets - What factors affect strength of an electromagnet?

Different materials have different resistance and electrical behaviours, when the same potential difference is applied to its terminals.

This does suggest that when the current increases in a material with a less resistively, the strength of an electromagnet also increases.  

Iron is magnetically soft, an ideal material for an electromagnet. It can change easily between being magnetised and demagnetised, therefore a perfect material for electromagnets, which needs to be turned on and off.

Steel is magnetically hard, an ideal material for permanent magnets.

Predictions

Experiment 1: How will varying the number of turns on the coil affect the strength of an electromagnet?

For experiment one, I predict that the strength of an electromagnet will increase, when the numbers of turns on the coil are increased.

Scientifically the strength of electromagnet will increase, when the current is supplied to the turns in the coil, because when electrons flow through the wire, a magnetic field is created around the wire. Looping the wire, many times will cause the magnetic fields to increase and concentrated within the loops, and therefore will strengthen the electromagnet. Similarly, the strength of an electromagnet will decrease, when the number of turns on the coil is decreased.

Experiment 2: How will applying different current affect the strength of an electromagnet?

For experiment two, I predict that as the current flowing around the core increases, the number of aligned atoms increases and the stronger the magnetic field becomes, hence stronger the electromagnet.

Scientifically the strength of an electromagnet will increase, when a larger current is applied. This is because electrons behave like tiny magnets, because when they spin in the same direction, a magnetic field is generated. The magnetic field will increase even more if the current applied is increased, because the number of electron and aligned atoms increase, a greater magnetic field is generated, from the spinning of the electrons, making a stronger electromagnet. Similarly as the current flowing around the core is decreased, the number of aligned atoms decrease and weaker the magnetic field becomes, and the strength of the electromagnet is decreased.  

Method

Experiment 1: The affect on the strength of an electromagnet, when varying the number of turns.

Apparatus required

• 2 Battery of 1.5v
• Few paper clips
• The inside of tissue role  
• Metre of Insulated wire (to wrap around)
• Iron bar

Procedure of the experiment

1. Take the wire and wrap around the tissue role’s core making a coil. Making sure that the two inches of unwound wire on each end is left.
2. Make sure that the wire is wrapped tightly and close together, place the iron bar inside the tissue role.
3. Connect the terminals of the batteries in series, with the two wire ends.
4. Using the core of the electromagnet, try picking up the paperclips.
5. Record the number of paper lips picked up.
6. Repeat each experiment three times with the different number of turns on core each time, to get an average.

Diagram 1, showing the position of the apparatus for experiment one.

Experiment 2: How will applying different current affect the strength of an electromagnet?

Apparatus required

• Power pack
• Few paper clips
• The inside of tissue role
•  Metre of insulated wire (to wrap around)
• Ammeter
• Connecting wire
• Iron bar

Procedure of the experiment

1. Take the wire and wrap around the tissue role’s core making a coil. Making sure that the two inches of unwound wire on each end is left.
2. Make sure that the wire is wrapped tightly and close together.
3. Connect the power pack with two wire ends.
4. Connect the variable resistor to the power pack.
5. Connect the ammeter in series.
6. Connect the electromagnet with the ammeter.
7. Connect the electromagnet back to the power pack to complete the circuit.
8. Used the resistor to vary the current to the desired value.
9. Check that this value is shown on the ammeter.  
10.  Using the core of the electromagnet, try to pick up the paperclips.
11. Record the number of paperclips picked up
12. Repeat each experiment three times, with different current values to get an average result.

Diagram 2, showing the position of the apparatus for experiment two

Safety measures

Safety is needed during any type of experiment carried out. Experiment I carried out, involved handling with electricity, therefore taking safety measures was an important part of experiment:

• Make sure that there was no bare insulation or any water near any electrical appliance to prevent electrocution.
• Make sure that too much current is not applied to the circuit, as a greater current can make the wire too hot, and cause a fire hazard.
• Make sure there is no water around the equipment and that hand is not wet when carrying out the experiment.
• Don’t touch the rheostat/variable resister, as it can get hot.

Fair test

Fair test is important, because it makes the experiment fair, and gives an accurate result.

In order to get a fair result, I tend to keep number of variables constant:

1. In experiment 1, I tend to keep the current voltage constant, as I am varying the number of turns. The reason to this is that more current produces more magnetic fields around the coil, so therefore affects the strength.

2. In experiment 2, I tend to keep the number of turns on the coil constant, as I am varying the current by using the power pack. The reason to this is that more turns produce more magnetic fields around the coil, so therefore affects the strength.

3. The material of the coil used in both experiment will be the same through out, as it can also make the results inaccurate, because different materials, if used with the same current will produce magnetic fields with different strengths, because the electrical conductivity of the materials are different form each other. The coil used in theses experiment is iron, because it can easily be magnetised and can be used in other experiments because it does not need to be demagnetised, ones being magnetised.

4. The way in which the wire is coiled. If the coils are coiled towards end, then one end will be more powerful than the other, and affect the results. I tried to keep the shape of the coil uniform in both of the experiments.

Table of results

The tables below show the results obtained form the experiments.

Experiment 1: How will varying the number of turns on the coil affect the strength of an electromagnet?

In this experiment the current applied is kept constant 1.5v

Experiment 2: How will applying different Current affect the strength of an electromagnet?

In this experiment the number of turns on the coil is kept constant 10 turns

Note: in analysis and evaluation section the statistics worked out refer to the average results, as they are the most reliable and accurate.

Method used to work out:

Average time = Total of three experiments

Analysis

I have decided to show my results, obtained from the experiment in a table, because a table give me an opportunity to organise my data into groups. The table also helps me simplify and analyse my data.

I have then decided to draw a line graph using my results, because a line graph is a simple and the most logical way of showing the chosen two factors that affect the strength an electromagnet. The line graph is also the best way of showing the trends and relationship between two dimensions. The data is also continuous therefore line graph is most appropriate.

The graph one shows the average number of paper clips attracted, when varying the number of turns. The line of best fit on graph one shows a positive correlation, which shows that an increase in the number of turns will attract more paperclips. The table of results and the graph one also support that, as the number of turns on the coil is increased, the average number of paper clips attracted increase. The line of best fit shows the trend.  When the number of turns on the coils is increased to 80 turns and a current of 1.5v (kept constant throughout) is applied, the average number of paper clips attracted is 23.33. This suggests the strength of electromagnet increases, when the numbers of turns on the coil are increased. Hence proves my hypothesis.

This is because, when the current is supplied to the turns in the coil, because when electrons flow through the wire, a magnetic field is created around the wire. Looping the wire, many times will cause the magnetic fields to increase and concentrated within the loops, and therefore will strengthen the electromagnet. Similarly, the strength of an electromagnet will decrease, when the number of turns on the coil is decreased.

The table of results and the graph one clearly concludes that the more turns on the coil, the stronger the electromagnet becomes. Therefore 80 number of turns around the coil, show a greater attraction of paper clips, hence the stronger the electromagnet. The graph shows a steady increase in the attraction of paper clips, as the turns were increased.

The graph two shows the average number of paper clips picked up, when varying the current. The line of best fit on graph two shows a positive correlation, which shows that an increase in the current will attract more paper clips. The table of result and graph two also support, that as the current applied is increased, the average number of paper clips increase.  The line of best fit shows the trend. When the current applied is increased to 5 amps, the average number of paper clips attracted was 20, during this experiment the number of turns was kept constant. This suggest that as the current flowing around the core increases, the number of aligned atoms increases and the stronger the magnetic field becomes, hence stronger the electromagnet.

This is because, when a larger current is applied. This is because electrons behave like tiny magnets, because when they spin in the same direction, a magnetic field is generated. The magnetic field will increase even more if the current applied is increased, because the number of electron and aligned atoms increase, a greater magnetic field is generated, from the spinning of the electrons, making a stronger electromagnet. Similarly as the current flowing around the core is decreased, the number of aligned atoms decrease and weaker the magnetic field becomes, and the strength of the electromagnet is decreased.  

The table of results and the graph one clearly concludes that the greater supply of current, the stronger the electromagnet becomes. Therefore 8 amps show a greater attraction of paper clips, hence the stronger the electromagnet. The graph shows a steady increase in the attraction of paper clips, as the current applied is increased.

Evaluation

I am pleased with my method and results as they turned out to be quite informative. The method I used was good, but could have been better, as there was one anomaly in my first experiment, when varying the number of turns. The method I used for the second experiment was good, as I didn’t get any anomalous results. The results achieved from both of the experiment, excluding the anomaly, when plotted on graph all lie close to a straight line, which suggest that my results were fairly accurate.  

The anomaly in experiment one may have resulted form a human error made during the experiment, for example; when varying the number of turns on the coil, the coil around the core may not have been uniform. This may have caused the anomaly, as it could make the magnetic fields around the core weak. The anomaly may also have been resulted, because the iron bar might have sided out slightly, causing the magnetic field to weaken.

During both of the experiment I also observed number of things. During the first experiment I noticed that, when the power pack was switched off on a particularly high number of coils, the paperclips were still attracted to the coil, even with out the current. From this I could only conclude that the charge is left over form the previous experiment in the iron, but that is unlikely as iron losses its charge quite quickly, so it is most probably the paperclips retaining their charge.  This must also mean that the next experiment must also be affected in some way, which might affect the next set of results. Another thing I observed during the experiment was that the size of paper clips and how much room they took up on the coil.  Technically the smaller the paper clip the more accurate the results, but I found that their wasn’t enough room on the coil to fit all the paper clips, so even if I wanted to test above 5 amps I wouldn’t be able to. This meant that if I was to carry out the experiment in more details, I would need a bigger coil; from this I could also see how the size of the nail affects the magnetism, compare to my old results.

If I were to change my experiment, I would try using iron fillings instead of paperclips to see whether it would give me more accurate and reliable results. Irons filling are appropriate, because they would be more accurate in weight as they are smaller. I would also use a better power pack, one which can exceed above 5 amps. This would help me obtain more results and a greater graph to see if my straight line continues on. I would also have a bigger coil, to be able to attract more paperclips, so that it would also have more turn on the coil and more paperclips attracted, which would again increase my results capability.

To increase the reliability of my results, I would use fresh paperclips after each test, because I believe that paperclips that have already been used in the experiment still carry the magnetic charge, which could distort the results.

I could carry out further work related to this investigation.  I could also investigate the material of the coil, which is another factor affecting the strength of an electromagnet. I could investigate this, by placing different materials, like iron, copper, and steel inside the core of the electromagnet, I would keep current and the number of turns constant. The strength will be tested, by the number of paperclips attracted. The evidence I should achieve is, when the current increases in a material with a less resistively, the strength of an electromagnet also increases.  

Overall I did enjoy investigating the aspects of electromagnet. I manage to prove my hypothesis, with my results, obtained during the experiment.