Uses of electromagnets
· Electric bells
· Telephones
· Sorting scrap metals (to extract iron, steel, nickel from others metals and non-metals)
Planning Experimental procedures
The quantity that I am intending to investigate in my experiment is the
strength of the electromagnet
The factors that affect the strength of an electromagnet are: The
temperature, current, length of the core, diameter, the thickness of the
wire used for the coils, how tightly the coils of wire are wrapped around,
the material and also the number of turns on the electromagnet.
I am only going to vary current in the experiment, all the other factors
I will keep constant
I have chosen to vary current because, the more turns there are, the more
powerful the magnet becomes and therefore the more domains there are. The
thicker the diameter is, the more domains there are in the middle and
therefore the stronger the electromagnet becomes.
The higher the temperature is, the easier it is for the domains to be able
to turn and line up. If you use a thinner wire it will cause more resistance
in the experiment. All of these factors will change the strength of the
electromagnet.
I decided to do current, as the others were more difficult to do.
Prediction
I predict that as he current increases the strength of the electromagnet will increase (get stronger).
Apparatus used: An electromagnet, power pack, ammeter,
an iron bar and electric scales.
To measure the strength of the electromagnet, first of all we had to
weigh the iron bar. We then switched the current on to flow through the
circuit. By taking a range of different readings off both the balance and
the ammeter, we established that as you increased the amount of current, the
iron bar got lighter. This is because the electromagnet was getting
stronger, pulling the iron bar up and taking the pressure off from the
electric scales. First of all I will set up the apparatus as planned, and I will take
readings. Then checking the variation in the weight
of the iron bar We also tested what was a safe distance for an
electromagnet from the iron bar-ten centimetres was too far, two centimetres
was too close, and five centimetres was a satisfactory distance.
Results table (Average)
Analysing Evidence & Drawing conclusions
To draw a conclusion from my graph, first of all I would divide it into
three sections: Section A (the bottom), section B (the middle) and section C (the
top). This would now make it easier to describe.
The first section (A) looks like it does because for the amount of current
put in. The graph then gets
steeper (section B); this is because all of the domains are now lining up. As the strength of the current goes up, the strength of the electromagnet goes up directly proportionate to it. In section C, all of the domains had lined up. Section
C was not drawn in on my graph because of the fact that there was not enough of a wide
range of readings available to be taken with the apparatus that I was given. The graph was not what we had expected; I was expecting to be drawing a straight-line graph. We thought that they would line up straight away. The graph was curved because as the current increased the resistance was greater so that there wasn’t a straight increase the in the current passing though the electromagnet, the greater the current the greater the resistance in the wire so was causing more resistance than when there was les current running through it.
Evaluation
In the experiment, the current changed quicker as it increased per centimetre. This made it fluctuate more, and it was therefore harder to be able to obtain accurate readings. After we had been carrying out the experiment for a while, the bar may have retained a
bit of magnetism if a large enough current was put through. There was also a change in the temperature of the bar-it heated up.
When doing the experiment we made sure that we turned it off after taking
each reading so as we kept control of the temperature in the experiment and
to avoid it heating up and affecting the experiment, making it unfair. There
was less chance of getting any anomalous results. We took an
average of the three results. It was a reasonably accurate experiment, and
if I repeated it I would get similar results.
If I wanted to make some improvements to the experiment, I would take the
results five times, and to a greater degree of accuracy of current and
weight loss (four decimal places or more). We also could have tried to keep
the temperature more constant by not leaving the current on between the
takings of readings and leaving it to cool.
To extend the investigation I could have tried varying the number of coils,
or another factor, keeping the current constant, then another variable and
comparing the results of varying.
By Liam Roberts 11S4©