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Electromagnets Investigation

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An electromagnet is a device consisting of a solenoid usually a cylindrical coil of insulated wire in which an iron core is placed. An electric current passed through the coil induces a strong magnetic field along the axis of the helix. When the iron core is placed in this field, microscopic domains that can be considered small permanent magnets in the iron align themselves in the direction of the field, thus increasing greatly the strength of the magnetic field produced by the solenoid. The magnetization of the core reaches saturation once all the domains are completely aligned, and an increase of the current in the solenoid has little further effect. When the current is switched off, the core retains only a weak residual magnetism.

The Domain Theory

The domain theory of magnetism suggests that a magnetic material such as iron contains within its structure tiny cells called domains and that mini molecular magnet exist inside theses domains.

In an unmagnetised piece of iron all the mini magnets within a particular domain point in the same direction but in each neighbouring domain they point in different directions. The result of this is that the magnetised effect of the domains cancel each other out.


In an unmagnetised piece of iron all the domains are lined up so that their magnetic effect reinforce each other.


Flemming’s left hand rule

Using Flemming’s left hand rule the direction of the force/motion can be predicted


...read more.


  1. Set up the experiment as shown on the diagram
  2. Get the nail and put 5 coils around it.
  3. Switch the power pack on and put it on 2 amps.
  4. Take the nail and put it near the paper clips.
  5. The nail should attract the paper clips towards it.
  6. Switch the power pack off and count the number of paper clips caught.
  7. Record the result and do the same for 4, 6, 8, 10, and 12 amps.
  8. Repeat the whole experiment another two times to make the results accurate by making an average..


For this experiment to be fair, I need to consider a few things:

  • Keep the number of turns the same when I am doing the experiment for the current.
  • Keep the current the same when doing the experiment for the number of turns.


Safety is a major aspect to any experiment:


I will use two different tables for the two variables; number of coils and the current.

Number of Paper Clips Caught

1st results

2nd results

3rd results


Number of Coils

5 coils

10 coils

15 coils

20 coils

25 coils

Number of Paper Clips Caught

1st results

2nd results

3rd results


Current (Amps)








I am going to repeat the experiment at three times. This is so it will enable me to make an average time.

...read more.


The way I did the experiment was that I put turns of coils on the iron nail and connect the wires to a power pack. I then took the nail near to some paper clips which attracted to the nail:


Using paperclips is not a good way of doing this kind of experiment because it takes time to count them, and you may miscount. So, if I had the opportunity to do the experiment again I will use iron fillings instead of paperclips. This method will not only be quick but also accurate because when you take the electromagnet near the iron fillings, it will attract them and you only have to weigh them, instead of counting.

To improve the experiment even more I could use a soft steel core instead of an iron core. This will improve the experiment because it will make sure that the core isn’t remained magnetically charged from the previous experiment, and so doesn’t produce any anomalous results.

I could also extend the experiment and see if the cross-sectional area of the coil effect the electromagnet. This could be done by………………………………………………

I also could also repeat the experiment four times instead of three, which will make the results eve more accurate, when making the average, which can be done by adding the four results and dividing the answer by four.

...read more.

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