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What Affects the Strength of Magnetism Exerted By an Electromagnet?

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What Affects the Strength of Magnetism Exerted By an Electromagnet?


I am going to investigate what factors affect the strength of magnetic field exerted by an electromagnet.  I will use a number of theories to plan my investigation.

Iron, Cobalt or Nickel become magnetic when their domains point in the same direction.  This is because all the N-poles add up at one end and the S-poles add up at the other end.  These N-poles and S-poles then form concentrated magnetic areas relative to their direction.  The will point towards ‘Magnetic North’.

This is the similar to what happens with lines of force.  When any of the three magnetic metals become magnetic, they exert magnetic lines of force.  These lines of force are called ‘Magnetic Fields’.  These lines of force exeunt from the ‘North Pole’ and are attracted to the ‘South Pole’, or any other metal with magnetic capabilities.

We can demonstrate the ‘lines of flux’ (lines of force) by using a compass.  A compass will follow the lines of flux from the North Pole.  This is possible because the compass needle is magnetic with a North Pole and a South Pole.  The North Pole of the needle is attracted along these lines of flux to the South Pole.  This also demonstrates that ‘Unlike Poles Attract’.  Like Poles (e.g. North and North) repel each other.  This can be established by bringing two North Poles together.  This can be achieved by magnetizing two pieces of metal, with magnetic capabilities, and cutting them in half.  We result in two pairs of North and South Poles.  Bringing the ‘Like’ poles together will result in the poles repelling each other.  This method would be suitable because using two magnets with both poles could indicate that the opposite poles were attracting!

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What is an ‘Electromagnet?’

An ‘Electromagnet’ is often a core of metal with magnetic capabilities (Iron, Cobalt or Nickel) in a coil of wire.  When the wire has no current flowing through, the metal possesses no magnetic ability.  However, when the current is passed through the wire, the core has magnetism induced into it.  This is because the wire is adjacent to the metal core.

Apparatus and Planning

I based the majority of my apparatus and method on my computerized preliminary investigation.  In this investigation I discovered that 3A (Three Amperes) is sufficient to gather relatively accurate results when performing the investigation on a small scale.

  • Paperclips Weighing 0.62g Each
  • Soft Iron Core Cylinder
  • Three Feet of Copper Wire
  • Mains Converter Outputs DC

It is vital that I used paperclips that were identical by size and mass.  Therefore, to keep my investigation fair, I weighed each paperclip used and compared sizes.  This was vital as the force of attraction is affected by the size of the paperclip.  This is because if the lines of flux have a larger surface area to attract, the consequential induced magnetism will be greater according to my domain theory.  The mass was also an important factor because paperclips are small; many domains deep into the paperclip’s matter will be aligned.

The optimal magnetism exerted from the electromagnet is affected by the number of charged coils of wire adjacent to a metal core’s surface.  Therefore, by increasing the number of coils you will increase the magnetism exerted.  You will also increase the strength by increasing the surface area of the core.  The magnetism exerted by a specific mass of a core should be relatively proportional to the number of coils coiled around the core.  I have chosen to use a cylinder core because of the large surface area.

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This could have been prevented by replacing all of the paperclips in the container with paperclips that have scrambled domains and no retained magnetism.

  • A total of 100 coils were wrapped around the soft iron core.  During the experiment it is possible for the coils to move.  The movement of the coils can affect the number of domains aligned in the core, thus altering the power of the electromagnet.  From this, numerous or single results can be affected.

The coils could be securely fixed and the electromagnet could be lowered by a vice to ensure the electromagnet is always lowered in the same position.

  • A soft iron core prevents the magnetism from the previous use to be retained.  However, some magnetism can still be retained of the core is not hit against a surface or heated to randomize the domains.

This action was not used in the method and could have affected the overall results similarly to the retained magnetism in the paperclips.


Although there were a few faults in the methodology used in the experiment, the results attained display a correlation and agree with the hypothesis on a whole.  The experiment could have been repeated to increase the reliability of the results, and the method could be changed to include the affecting factors stated in the evaluation.

Proportionality was shown in the results and the hypothesis was proved true.  To conclude, the Resistance, Voltage and Coils around the soft iron core influence the attracting strength exerted by an electromagnet.  Overall, the strength of an electromagnet is determined by the number of domains aligned in the core!

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