The Strength Of An Electromagnet Essay, Research Paper
The strength of an Electromagnet
Planning Experimental procedures
"h The quantity that I am intending to investigate in my experiment
is the
strength of the electromagnet
"h 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.
"h I am only going to vary current in the experiment, all the other
factors
I will keep constant
"h 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.
"h I decided to do current, as the others were more difficult to do
"h I believe that when I do the experiment, proportionally as the
current
increases, the strength will increase.
Force (N)
Current (A)
"h I have made this prediction because as you increase the current, you
will
induce more domains to line up- and if its proportional, you would then
double your current which would therefore double the domains (force). If you
were to cut a magnet in half, it doesn¡¦t destroy it, in actual fact two
magnets are created.
If you wanted, you could continue cutting the magnets in half each time
therefore making the magnets smaller and smaller. In theory, if we used an
extremely sharp, but still small blade, we would be able to on cutting
magnets in half until we reached a limit-this would be called a domain and
is about 1/1000th mm long and would consist of about 10 thousand million
atoms.
An unmagnetised iron would look like this:
Using the current in the coils, you would be able to re-align some of
the
domains. If you did this and as a result more of the domains were pointing
in the same direction, then the iron would have become a weak magnet.
A weak magnet would look like this:
When you switch off the current, the domains would return back to a random
set up. Obviously, if you were to line more domains up, the magnet would
bcome much stronger, until you were to reach a state where you had aligned
all the possible domains up.
A fully magnetised magnet would look like this:
"h Apparatus used: An electromagnet, powerpack, variable resistor,
ammeter,
an iron bar and an electric balance. The following diagram is how we set the
experiment up:
"h 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 balance.
"h First of all I will set up the apparatus as planned, and I will take
readings ranging from 6A to 0.5A. Then checking the variation in the weight
of the iron bar. I did some preliminary experiments so that I could find out
the range of the current, and how much voltage
and also exactly how far the electromagnet should be away from the iron bar.
"h I did a preliminary experiment before the actual experiment
"h I tested what was a safe current. I found out that a current up to
six
amps was satisfactory. We also tested what was a safe distance for an
electromagnet from the iron bar-ten centimeters was too far, two centimeters
was too close, five centimeters was a satisfactory distance.
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, only
a few of the domains had lined up.
My second reading that I took was inaccurate, so on my graph I have circled
it, and discluded it in the drawing of the curve. 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, as I wrote in my planning that I
was expecting to be drawing a straight line graph. This prediction was wrong
because we had not expected the domains to take time to line up. We thought
that
they would line up straight away.
Evaluating Evidence
In the experiment, the current changed quicker as it increased per
centimeter we pushed the variable resistor. 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 an anomale in the experiment because we took an
average of the three results. It was a reasonably accurate experiment, and
if I repeated it I would get similar results. I can justify all but the
third section on my graph (C) because I didn¡¦t go to a high enough voltage,
but if I did I would have obtained the ¡§leveling off zone¡¨ because other
people using a high enough voltage did.
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. We should also have zeroed the
balance before taking each reading.
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 those others. I could also have tried using
iron filings for an example to see if different results were given.
Biblography
Books that I have used for help are: A new and physics by D.Brybant and
D.E.Kershaw also Advanced physics fields, waves and atoms by T.Duncan.