Atoms line up into parts of the magnetic with similar directions called domains. This is because the earth has a magnetic field and the atoms in the metal all follow these magnetic lines and form these domains (force). This is similar to what happens when an electromagnet is formed.
Preliminary experiments; I did some preliminary experiments so that I could find out the range of the current, and how much voltage was needed in the experiment, and also exactly how far the electromagnet should be away from the iron bar. I tested what was a safe current. I found out that a current up to 2.2 amps was satisfactory. I also tested what was a safe distance for an electromagnet from the iron bar - ten centimetres was too far, two centimetres was too close, five centimetres was a satisfactory distance.
Method: I will set up the apparatus in a circuit form as shown below in the diagram. I will switch the current on to flow through the circuit. I will wrap insulated wire round an iron bar and the ends of the wire will be connected to a battery by croc clips. By taking a range of different readings, of both the force of the attraction and the current (Amps). I am only going to vary current in the experiment, all the other factors I will keep constant. I will repeat each experiment two times for accuracy and to decrease the change of error. I am going to use 200 coils round the iron core because this amount is sufficient. I will take readings ranging from 1.7A to 2.2A using the ammeter. The Newton meter will test the strength of the magnet as the current increases. To obtain my results a table will be used to record them. The results are below.
1st test.
2nd test
The average found from the 1st and 2nd.
Conclusion: To draw a conclusion from my graph, first of all when you switch off the current, the coils would return back to a random set up. Obviously, if you were to line more coils up, the magnet would become much stronger, until you were to reach a state where you had aligned all the possible coils up.
I think that the more current that goes through the wire, the greater the electromagnetic pull of the soft-iron core will be. This is because the current going through the wire makes the soft-iron core is the factor that induces electromagnetism, as so when there is more current, there will be more electromagnetism. This is the same with the number of coils, with the electromagnet, the more power is returned. The return and investment are not directly proportional.
My second reading that I took was inaccurate, so on my graph I have circled it, and disclosed it in the drawing of the curve. The graph then gets steeper, this because as the strength of the current increases the strength of the
This prediction was right and I am satisfied will these results electromagnet increases the magnetism.
Safety Precautions; We will make sure that there is no bare insulation or any water near any electronic equipment to prevent electrocution.
Evaluation:
In the experiment, the current changed quicker as it increased per centimetre I pushed the variable resistor. This made it fluctuate more, and it was therefore harder to be able to obtain accurate readings. After I had been carrying out the experiment for a while, the iron bar may have retained a
bit of magnetism if a large enough current was put through. There was also a change in the temperature of the iron bar-it heated up.
When doing the experiment I made sure that I turned it off after taking each reading so as I kept control of the temperature in the experiment and to avoid it heating up and affecting the experiment, making it unfair. There was less chance of getting an anomaly in the experiment because I took an
average of the three results. It was a reasonably accurate experiment, and if I repeated it I would get similar results. On my graph I had no anomalous results they all fitted and where plotted properly.
If I wanted to make some improvements to this experiment, I would take the results five times, and to use a computerized Newton meter instead of the spring product one. I also could have tried to keep
the temperature more constant by not leaving the current on between the takings of readings and leaving it to cool. I should also have zeroed the balance before taking each reading.
To extend the investigation I could have tried varying the number of coils, or another factor, keeping the current constant, then another variable and comparing the results of varying those others. I could also have tried using iron filings for an example to see if different results were given.
Bibliography:
Books that I have used for help are: A new and physics by D.Brybant and
D.E.Kershaw also Advanced physics fields, waves and atoms by T.Duncan