The Strength Of An Electromagnet Essay Research

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


I will keep constant

"h I have chosen to vary current because, the more turns there are, the


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


"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


increases, the strength will increase.

Force (N)

Current (A)

"h I have made this prediction because as you increase the current, you


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


An unmagnetised iron would look like this:

Using the current in the coils, you would be able to re-align some of


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,


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 was needed in the experiment,

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


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


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


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


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


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.


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.


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