Strength of an Electromagnet.

Strength of an Electromagnet

Introduction

The basic idea behind an electromagnet is extremely simple: By running electric current through a wire, you can create a magnetic field.

A Regular Magnet
Before talking about electromagnets, let's talk about normal "permanent" magnets like the ones you have on your and that you probably played with as a kid.

You likely know that all magnets have two ends, usually marked "north" and "south," and that magnets attract things made of . And you probably know the fundamental law of all magnets: Opposites attract and likes repel. So, if you have two bar magnets with their ends marked "north" and "south," the north end of one magnet will attract the south end of the other. On the other hand, the north end of one magnet will repel the north end of the other (and similarly, south will repel south).

An electromagnet is the same way, except it is "temporary" -- the magnetic field only exists when electric current is flowing.

An Electromagnet
an electromagnet starts with a (or some other source of power) and a . What a battery produces is electrons.

If you look at a battery, say at a normal D cell from a flashlight, you can see that there are two ends, one marked plus (+) and the other marked minus (-). Electrons collect at the negative end of the battery, and, if you let them, they will gladly flow to the positive end. The way you "let them" flow is with a wire. If you attach a wire directly between the positive and negative terminals of a D cell, three things will happen:

Electrons will flow from the negative side of the battery to the positive side as fast as they can.
The battery will drain fairly quickly (in a matter of several minutes). For that reason, it is generally not a good idea to connect the two terminals of a battery to one another directly. Normally, you connect some kind of load in the middle of the wire so the electrons can do useful work. The load might be a , a , a or whatever.
A small magnetic field is generated in the wire. It ...

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Electrons will flow from the negative side of the battery to the positive side as fast as they can.
The battery will drain fairly quickly (in a matter of several minutes). For that reason, it is generally not a good idea to connect the two terminals of a battery to one another directly. Normally, you connect some kind of load in the middle of the wire so the electrons can do useful work. The load might be a , a , a or whatever.
A small magnetic field is generated in the wire. It is this small magnetic field that is the basis of an electromagnet.

The part about the magnetic field might be a surprise to you, yet this definitely happens in all wires carrying electricity. You can prove it to yourself with the following experiment. You will need:

An AA, C or D cell battery
A piece of wire (If you have no wire around the house, go buy a spool of insulated thin copper wire down at the local electronics or hardware store. Four-strand wire is perfect -- cut the outer plastic sheath and you will find four perfect wires within.)
A compass

Put the on the table and, with the wire near the compass; connect the wire between the positive and negative ends of the battery for a few seconds. What you will notice is that the compass needle swings. Initially, the compass will be pointing toward the Earth's North Pole (whatever direction is for you), as shown in the figure on the right. When you connect the wire to the battery, the compass needle swings because the needle is itself a small magnet with a north and south end. Being small, it is sensitive to small magnetic fields. Therefore, the compass is affected by the magnetic field created in the wire by the flow of electrons.

The figure below shows the shape of the magnetic field around the wire. In this figure, imagine that you have cut the wire and are looking at it end-on. The green circle in the figure is the cross-section of the wire itself. A circular magnetic field develops around the wire, as shown by the circular lines. The field weakens as you move away from the wire (so the lines are farther apart as they get farther from the wire). You can see that the field is perpendicular to the wire and that the field's direction depends on which direction the current is flowing in the wire. The compass needle aligns itself with this field (perpendicular to the wire). If you flip the battery around and repeat the experiment, you will see that the compass needle aligns itself in the opposite direction.

Because the magnetic field around a wire is circular and perpendicular to the wire, an easy way to amplify the wire's magnetic field is to coil the wire, as shown below:

For example, if you wrap your wire around a nail 10 times, connect the wire to the battery and bring one end of the nail near the compass, you will find that it has a much larger effect on the compass. In fact, the nail behaves just like a bar magnet.

However, the magnet exists only when the current is flowing from the battery. What you have created is an electromagnet! You will find that this magnet is able to pick up small steel things like paper clips, staples and thumb tacks.

Prediction

I Predict that the more coils there are on my iron horseshoe shape the stronger the electromagnet will be. I think this because the more wire there is the more electric current flowing through the iron horse shoe shape core.

Plan

I plan to find out if the number of coils will effect the strength of the electromagnet. I will keep the thickness, mass, weight, voltage, number of paper clips the same the only thing I will change is the number of coils. The way I will find the strength is by seeing how many paper clips my electromagnet will pick up each time. I will do this test 5 times for each number or coils. The number of coils will go from 5 to 60 going up in 5’s.

Method

To start with I need wire (which I will be keeping the thickness, mass/weight all the same), an iron horse shore shape core, an electric current (volt kept the same all through the experiment), a voltmeter (to check the current stays the same) and paper clips.

First I wrap the wire around the iron core 60 times. Then I connect the wire to the mains and pass a voltage of about 4 volts through the wire. Then I make a pile of paper clips and place my electromagnet into the pile. After 10 seconds I pull out the electromagnet and place on the table away from the other paper clips and turn off the electric current. I now have to count the number of paper clips the electromagnet could hold. I repeat this 4 more times before removing 5 of the coils. I do the same experiment 5 time for each number of coils.

Results

For results see the results table.

Analyzing

See results graph.

I believe that this experiment was successful my results were positive and gave my a good graph which shows that the results were complete and support my prediction that the more coils there are on my iron horseshoe shape the stronger the electromagnet will be. I think this because the more wire there is the more electric current flowing through the iron horse shoe shape core.

I conclude that the more coils the stronger the electromagnet becomes. Therefore if I had 100 coils around my iron horse shoe shape core it would be even stronger but if I had only one coil it would be very weak or may not even work.

Evaluation.

This experiment was successful my results support my prediction that the more coils there are on my iron horseshoe shape the stronger the electromagnet will be. I think this because the more wire there is the more electric current flowing through the iron horse shoe shape core.

My experiment went the way I planned but if I had to redo this I would improve my results and make them more accurate by taking more results for a more exacted average.