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Find out the factors affecting the strength of an electromagnet.

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AIM: The aim of this investigation is to find out the factors affecting the strength of an electromagnet.


Magnetism is the tendency a metal such as iron, steel and cobalt have to attract other metals e.g. pins.

        Magnetism arises as a result of the motion of charged particles called electrons in the wire. In most substances the effect of this motion cancel out, but in ferromagnetic substances they do not.

        When insulated wire is wrapped round an iron nail and the ends of the wire are connected to a battery, and the nail becomes capable of picking up iron filing or paper clip. The nail is magnetised by the current in the wire. If the battery is disconnected then the clips will fall of. This is because they are not a permanent magnet; they are called temporary magnetism.

        The iron filings cluster around the end of a magnet because a magnet behaves as if all its magnetism were concentrated near its ends.

These place were the magnetism appear to be concentrated are called the poles of the magnet.


IF a piece of ferromagnetic substance is made to touch or brought near to the pole of a magnet, it becomes a magnet itself. This is called induced magnetism.

        This end of the substances nearest to the inducing pole has an opposite pole inducing in it.

...read more.


Nail, Ammeter, Wires, Lab-Pack, and Paperclips.



To get meaningful and fairly accurate results I took the average from two results. The reading  was taken from between 0.10 Amps and 1.00 Amps (went up in even Numbers), so I had a sufficient range to find any patterns or trends.

I repeated my results five times with different numbers of coils each time just to backup any patterns.

For safety I used a thin black wire , which I think is better because it could allow more current going through it with out burning up. After I had took a reading I turned the Lab-Pack of each time so the nail would not get too hot to handle.

Fair Test

The variable that I changed is the currant through the wire and the numbers of coils of the wire.

The variable, which I kept the same to ensure a fair test are:

  • length of nail
  • surface area of nail head.

The thing that I will measure is the amount of paperclips that the head of the nail picks up when magnetised. The weight of a paperclip was 0.5g. I used only the paperclips, which weighed 0.5g to ensure it was fair test.


In my investigation I found out that as I increased the current the amount of paperclips picked up had increased and as the number of coils decreased the number of paperclips picked up decreased.

...read more.


If I had to do this investigation again then I would improve it by going only up to 10 amps for safety reasons and I take more care when I was measuring the weight of the paperclips so I wouldn't get any odd ones that should not be there.

I could use something which gave me more accurate readings of the currents flowing through the wire and a power pack which didn't give slight changes in the current given out and would be more steady.

To improve the reliability of this investigation I would change the way in which I did my experiment because I found it to be a little unreliable as in the table above. To improve the reliability I would put the paper clips on a top-pan balance and put the electromagnet at a certain height and calculate the decreases of weight on the top-pan balance to the strength of the electromagnet. I would take a range of readings from certain heights and take an average for each one. If a possible trend appears I could prove the trend by repeating the experiment with a different amount of current passing though the electromagnet.

The diagram shows how I will set up the apparatus for the experiment.

The electromagnet will attract the paperclips and there will be a change in weight on the top pan balance and I can use that to see how current effects the  strength of magnetism.



...read more.

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