In this experiment I intend to find out what affect the amount of turns in the coil of a solenoid, has on an electromagnet.

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Physics Coursework

Electromagnetism Investigation

Aim

In this experiment I intend to find out what affect the amount of turns in the coil of a solenoid, has on an electromagnet.  

Previous Scientific Knowledge

I know that a steel bar magnet emits a magnetic field flowing from its North to South Pole.  These can be created by magnetising a piece of steel, which aligns the metals molecular magnets; thus strengthening the field.  These will remain magnetised because steel is magnetically hard, iron however is magnetically soft and once magnetised, will soon lose those properties.  

This makes iron the ideal substance for an electromagnet because it can be turned on and off.  A current passing through a wire generates a magnetic field and if an iron core is placed inside a solenoid (coil of wire) it will become an electromagnet, amplifying and increasing this field with its own magnetic properties.  While a current passes through the electromagnet, it has become like a bar magnet with its magnetic field flowing from the North to South Pole.  If the current is stopped the iron immediately loses its magnetism and if the current is reversed the poles will change ends.  

These devices are perfect for making magnetic cranes can pick-up, move and then drop suitable metal objects.  So they have much use in the modern world.  

I believe that the factors that affect the strength of an electromagnet are:

  • The strength of the current; which varies with the strength of the magnet respectively

  • The purity, or rather the exact composition of the core (size, element/compound, purity)

  • The composition of the solenoid (size, element/compound, purity)

  • The size of the turns in the coil

  • The number of turns the coil has

I am not however, wholly convinced that the number of turns in the coil carries a direct relationship with the magnets strength and so I will investigate it

Hypothesis

I am not sure whether the amount of turns in the will affect the magnets strength whatsoever, but my guess would be that it does.  There are of course other factors to consider, the wire will be kept the same length each time and the current passing through will be the same.  These are precautions to make the experiment a fair test, but they make me think that, as these factors are the same there’s no reason for the magnets strength to alter.  With this in mind I am making the prediction that the more turns in the coil the weaker the magnet will become.  

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I think this will happen because the tighter coiling of the wire may obstruct the flow of the current and lessen the magnets strength.  Having a large amount of turns may also have a negative affect on the iron’s molecular magnets; (atoms in a small range of metals that produce magnetism) they may become aligned differently and in a sense ‘confused’ causing them to be less efficient.  The effect I think this could produce is that the molecular magnets would be told to align in different places so that they would be aligned incorrectly, thus making the magnet weaker. ...

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