Investigating the factors affecting the strength of an electromagnet.

Investigating the factors affecting the strength of an electromagnet

Background Knowledge:

The theory of magnetism is the only way to explain the process of magnetising an object. In an unmagnetised piece of iron the domains are pointing in numerous directions, which results in them cancelling each other out.

However, a magnetised piece of iron would have all the magnetic domains pointing in all the same direction. This is due to the north poles being at one end and the south poles at the other end. The domains are actually extremely small atomic magnets that line up with each other to form groups, called domains. All iron and steel are made up out of millions of these domains.

The magnetic field is the area around a magnet where it has a magnetic effect. The shape of a magnetic field can be determined by placing a thin layer of iron filings over paper with a bar magnet underneath. When the paper is gently tapped the iron filings act like tiny compasses and point themselves along the lines of flux. The magnetic field of an electromagnet is the same as a bar magnet and it looks like this:

Electricity has a magnetic effect; a wire carrying a current has a magnetic field round it. The magnetic field around a wire is in the shape of circles. The magnetic effect can be strengthened by:

-Using a larger current

-Using more turns of wire on the core

-Using a soft iron core

-Bringing the poles together

A circular magnetic field will develop around the wire. The field weakens as you move away from the wire, the field is perpendicular to the wire and the fields direction depends entirely on the direction of the current as it flows through the wire. The best way to amplify a magnetic field is to coil the wire.

This produces an electromagnet. Coiling the wire around a soft iron core increases the magnetic effect. When an electric current flows through the coil it becomes a magnet.

Aim:

I have decided to investigate increasing the strength of the electromagnet and therefore the magnetic field range of the electromagnet by varying the amount of coils present on the length of the electromagnet. In addition to this I will keep the amount of coils constant, 40 coils, and vary the current to see if this affects the strength of the electromagnet.

Method:

I will construct the ...

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This produces an electromagnet. Coiling the wire around a soft iron core increases the magnetic effect. When an electric current flows through the coil it becomes a magnet.

Aim:

Method:

I will construct the electromagnet by coiling insulated wire around the length of a long nail made of iron and stripping the two ends of the insulating plastic. These ends will then be connected with crocodile clips to two main wires joined to the battery. When varying the charge I will add an ammeter to the circuit to enable me to take accurate readings of charge.

To actually test the strength of the electromagnet, I will lay it in a pile of paperclips and turn on the electromagnet via the power pack and see how many paperclips the electromagnet has been able to attract. This will be measured at a constant current of 6.4 amps and the variable, the amount of coils will be measured at 10, 15, 20, 25, 30, 35 coils. I will carry out both experiments twice to try and gain more accurate results and acquire a full picture of the experiment.

Equipment:

Power pack
Wires (connecting)
30 paperclips
Iron nail
Wire (to coil)
Ammeter
Crocodile clips

Fair testing:

The current would be likely to change so I will keep it constant by observing the ammeter and correcting any fluctuations instantly. The soft iron core I use will be the same throughout the experiment so it doesn’t affect the magnetic strength of the electromagnet. The shape of the coils will be uniform and they will be evenly spaced. This is because if I keep the coils at one end only then this end will be more powerful than the other and I twill affect the results. The paperclips will be the same type and size so that they are not harder to attract, or easier as this would affect the results also.

Prediction:

Due to my background knowledge I predict that with the increase in the number of coils, the electromagnet will become stronger. This is because every turn of coil has its own magnetic field. When there are more turns in the same area, the coils magnetic fields overlap and this creates a stronger force.

The increase in current put into the electromagnet will increase its force also. This is because as more power is introduced to each coil, its magnetic field is increased and strengthened, causing the magnetic field to extend its previous limits and be able to attract more paperclips.

Results:

-Increasing coils when current was a constant of 6.4 amps

-Increasing current when number of coils was a constant of

Conclusion:

My results show that the increase in current and increase in coils both result in a stronger magnetic field and therefore a stronger electromagnet. From my results, I can see that the more coils there are around the Iron Core the stronger the magnetic field becomes. This proves my prediction; I had confidently predicted that any increase in the number of coils would strengthen the magnetic field itself.

Due to my background knowledge I had predicted that with the increase in the number of coils, the electromagnet would become stronger. This was because every turn of coil has its own magnetic field. When there are more turns in the same area, the coils magnetic fields overlap and this creates a stronger force. In other words I had predicted that it strengthens the magnetic field due to the wire having its own magnetic field around the end of each of the tips of the wire. As the wire is bent into a coil this encloses the magnetic field allowing the field to over lap creating a more concentrated magnetic field. This is what increases the strength of the magnetic field.

Both graphs resulted in a rough linear pattern and I can clearly determine that with an increase in both factors there was an increase in the strength of the electromagnet and therefore the amount of paper clips was able to attract.

I had also investigated increasing the current flowing through the electromagnet and seeing if this allowed the Iron Core to attract more paper clips. I had predicted that increasing the current would also affect the strength of the magnetism. This was because the increase in current put into the electromagnet increased its force. This is because as more power is introduced to each coil, its magnetic field is increased and strengthened, causing the magnetic field to intensify and grow allowing more paperclips to be attracted.

Evaluation:

The experiment I chose in my investigation was a good method to use as it effectively illustrated my prediction and was fairly simple to construct and carry out.

The results were very accurate and I had no anomalies, I think this was because I was very careful in trying to maintain one variable only and keeping all other factors constant by using, for instance, an ammeter to observe the current in a lot of accuracy.

The method may not have been entirely accurate as I am not sure that using paperclips to ascertain the electromagnets strength was the most accurate method, this is because it is hard to attach the paperclips once they have reached a certain length although this could have been because the magnetic field only reached so far. I am not sure how the method could be improved to gain more accurate results although possibly using a different material would be advisable.

Despite these queries I am certain that my results firmly support my conclusion as they match up with my background knowledge, prediction and follow a very clear pattern.

Further work could include varying the core used in constructing the electromagnet; I could investigate what makes the electromagnet stronger and weaker in the form of core material.

Lucy Gould 25th February 2002