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What factors affect the strength of electromagnetism?

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Sreekar Charlu VSP

Physics Coursework

What factors affect the strength of electromagnetism?



A home made magnet is essentially a metal core, with a wire coiled around it. The core should be a ‘soft’ metal, for example soft iron. A ‘soft’ metal is one that is easily magnetised and demagnetised, and a ‘soft’ iron core increases the field strength. A wire coil that carries current is called a solenoid, and this solenoid is wound around the soft iron core. When a current is passed through the circuit, and the coil, a magnetic field is produced at the centre. This aligns the particles in the iron core, which are tiny magnetic domains pointing in all directions in the absence of current, in one direction. A magnetic field is produced around the electromagnet – a magnetic field is a region where magnetic materials (e.g. iron and steel) and also wires carrying a current experience a force acting on them. Magnetism is said to be induced in the soft iron core, that is, the soft iron core becomes magnetised. It is electricity through the coil and the magnetism that it induces in the iron core, which give it the name electromagnet.

I used the book “Physics for You” by Keith Johnson.

De-magnetised metal

Magnetised Metal


There are numerous factors but I will talk about the three main factors.

  • The number of turns on the coil
  • The current through the coil
  • Material of core

Here, only one factor will be investigated, which is the current through the coil.

...read more.


  1. With sellotape secure the wire in place at each end of the core, but at the end tip of the magnet where you will be placing the Newton meter, leave that free of sellotape.
  1. Clamp the electromagnet using the wooden clamp stand.
  1. Using the variable resistor, measure 0.50A.
  1. Using the 1N Newton meter, place on top of electromagnet, which is sellotape free, and pull gently.
  1. Record result.
  1. Repeat steps 6→8, using the different currents.
  1. Once done, repeat whole experiment twice so that you have done it three times.

How to keep the experiment a fair test

  • While I alter my independent variable I will have to keep all the other variables constant, e.g. the number of coils: - if you change the number of coils while doing the experiment it can affect your results by either increasing or decreasing the force exerted.
  • I will have to use the same equipment all the way through, including the electromagnet because any piece of equipment may have a flaw in it, and if changed, can affect the results.
...read more.


        The experiment could be extended by doing it with a larger spread of currents and up to a higher level of currents. This would have tested the prediction even further and may have proved or disproved it conclusively.

        The experiment was a fair test because all the variables were kept constant except for the current (the test variable). The experiment was accurate in my opinion.

        There were no anomalous results. The evidence is definitely good enough to support my conclusion as they are clear and simple, but I have also explored the detail of my conclusion, and any contrast between my prediction and results.

        The prediction stated that the iron core held a certain limit for the amount of magnetic field it could exert, irrespective of whether I increased the current further or not. This would explain the predicted levelling off, which was expected by me to appear on the graph.

...read more.

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