The aim of my experiment is to see what factors affect electromagnetism the most so as to give the best electromagnet in an experiment.

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Nicholas Marshall 10A Monday 1st July 2002

Physics Coursework- Electromagnetism

Aim-

The aim of my experiment is to see what factors affect electromagnetism the most so as to give the best electromagnet in an experiment. The factors I will use are: the number of coil wraps around the iron nail and the amount of current in the circuit. It is these factors that I will use to see which one gives the best electromagnet.

Scientific Knowledge-

How to get an electromagnet-

When an electric current flows through a coil of wire it sets up a magnetic influence or 'field' around the wire. The more turns of wire there are in the coil and the bigger the current, the stronger this magnetic field will be. An easy way to wind the wire is around an object and a winding like this is called a solenoid; if now an iron core is put through the hole in the coil it will become an electromagnet when a current is sent through the wire around it. The reason for using iron is that it concentrates and strengthens the magnetic field.

An Electromagnet in Electron Terms-

This part is quite simple. A current is made up of electrons, so when you say a current flows you could also say when electrons flow. So if a current creates a magnetic field then the electrons also create a magnetic field. So the flow of electrons gives a magnetic field, which in turn creates the electromagnet. So the electromagnet can be traced directly back to the electrons within a wire.

Magnetic Field-

If one considers the circular magnetic field round each short length of wire in the flat circular coil, it can be seen that the field adds up through the centre of the coil. This leads to a strong field through the coil but a weak one outside it (see diagrams).

A solenoid may be considered as a series of flat circular coils, each a little spaced apart from one another on a common axis. Each turn of insulated wire gives a magnetic field similar to that of a flat circular coil. The fields between neighbouring turns oppose one another and cancel, but the fields along the common axis reinforce, producing the pattern shown below.

I can say from this that because the magnetic field occurs most strongly on the inside of the circular wire that if an object of a specific material is placed through the circles then a magnetic field will be induced into it, which is why it becomes an electromagnet.

From these quotes I also know now that the magnetic field only occurs near and inside the coil wraps. Therefore magnetism will also be strongest in those same places.

Plan-

From my scientific knowledge I can make a reliable plan.

Equipment-

First of all the equipment, I need:

An electric current, so a power pack,

The coil to create the solenoid,

An iron nail to create the electromagnet,

And some wires and crocodile clips to connect the circuit together.

Some equipment to measure and control the experiment will also be needed, so an;

an ammeter to measure and...

either the power pack can control what current it lets through or a variable resistor (which also controls what current is let through but is an extra item within the circuit). Of the two the variable resistor is more accurate.

And lastly some equipment to measure the power of the electromagnet (this will be found out after further analysis).

Method-

Using the equipment above I can create a fair and reliable circuit. To make it I will connect the left side of the power pack to an ammeter with a wire. From the other side of the ammeter I will use another wire to connect the ammeter to the solenoid. This solenoid will have an iron nail through it so as to create the electromagnet. On the opposite end of the solenoid a wire will connect it to the right side of the power pack thus completing the circuit. If I will include a variable resistor it will go in between the power pack and the solenoid/ electromagnet using an extra wire. After the circuit is complete I will switch the power pack on to get a current flowing through the solenoid. To create the electromagnet I will basically wrap a piece of wire around an iron nail. The diagram below explains it in a simpler form.

Diagram-

Ammeter

Power pack

:+ x amps crocodile clips Coil wrapped

around the nail

x amount of times.

Variable resistor

The dotted line above in the diagram shows where I will include the variable resistor if I use it.

At the moment all I've talked about so far in my method is how I will make the experiment. I will now say how I will do the experiment. First of all before I start I will record all the experiments factors, which includes:

. Recoding the current in amps and...

2. recording the number of coil wraps.

When doing the test I will have to find a suitable method to measure how good the electromagnet will be when varying the factors. Since it is the magnetism that I am experimenting on and that a main point of magnetism is its ability to attract other objects I think that the best way to test it out is by putting certain amount of objects onto the electromagnet. The bigger number of the objects that the electromagnet can hold on to the stronger and more efficient it is, which is the whole aim of my experiment. The objects will have to be big enough to handle (as I don't have tweezers) but small enough to make accurate measurements on. After some thought I think that paperclips are the best objects to use as they are attracted to electromagnets and can be measured in mass and number, they are also easy to hold and small enough to get accurate enough recordings on. Therefore the efficiency of the electromagnet will be measured in grams (the mass of all the paperclips the electromagnet can handle).

To get recordings of how the number of coils affects an electromagnet and how the current affects an electromagnet I will have to do two separate tests comparing the final results afterwards to see which is the most efficient factor to make the electromagnet stronger. To get the results of these two factors I will have to vary them within separate tests. To increase the accuracy of my results I will also repeat these tests.

Experiment that will be used to test how much a varying current affects an electromagnet-

In the varying current experiment once the circuit is set up and the initial amps and coil wraps are recorded I will place paperclips onto the electromagnet and see how many will stay onto it by magnetism. These numbers of paperclips will then be recorded. The current will then be increased using the variable resistor or the power pack and the amps recorded using the ammeter but I will keep the coil wraps the same amount. Paperclips will again be placed onto the electromagnet again and then the number that stays in place will be recorded again. This will be repeated up to a suitable amount of times (an exact number of test repeats will be found in the preliminary test).

Experiment that will be used to test how much you can affects an electromagnet by varying the amount of coil wraps around the iron nail -

When doing the varying coil wraps experiment I will do exactly the same as above but instead the number of coil wraps will be increased and the current will remain constant.

It is in the varying current experiment that the variable resistor may be used (this also will be determined within the preliminary test).
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Fair Test-

When doing the experiment I must keep the factors that remain constant the same at all times. If they change then the electromagnet's performance may be hindered or increased both of which lowers the reliability of the results. This is called keeping it a 'fair test'. To keep the experiment as fair as possible I will have to do certain things. The most obvious thing to keep constant is the other variable that I am not changing, so when in the varying current test I must keep the coil wraps the same amount, the same ...

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