# Electromagnets

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• Published : November 8, 2005

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BACKGROUND

An electromagnet is a device in which magnetism is produced by an electric current. British electrician, William Sturgeon invented the electromagnet in 1825. The first electromagnet was a horseshoe-shaped piece of iron that was wrapped with a loosely wound coil of several turns. When a current was passed through the coil; the electromagnet became magnetized and when the current was stopped the coil was de-magnetized.

Sturgeon displayed its power by lifting nine pounds with a seven-ounce piece of iron wrapped with wires through which the current of a single cell battery was sent. Sturgeon could control his electromagnet; this was the beginning of using electrical energy for making useful and controllable machines and laid the foundations for large-scale electronic communications.

ASSIGNMENT OBJECTIVE

Using this theory, we were able to produce an electromagnet, which was the purpose of this assignment. However, the second component was not only to have a working magnet, but to make the magnet as most powerful as possible. We were required to investigate one variable and experiment with this variable to produce the most powerful magnet possible.

The variable that I investigated was; how does the number of coils affect the strength of the magnet? To be able to experiment with this variable, I was required to use the same materials for each magnet which composed of: Ferrite Soft Iron Core (50 grams, 100mm in Length)

Coated Copper Wire (0.630mm Width)

My hypothesis was that, the more number of coils wound around the soft iron core, the stronger the magnet would be and a proportional linear relationship would be present. That is, it would be able to pick up more staples that one with fewer coils.

EXPERIMENTING WITH THE VARIABLE

I made 3 magnets, each with a different number of coils to experiment my variable. To trail the strength of each magnet, I connect two 1.5V D-Cell batteries which provided me with a total of 3V. To then compare the relative strengths, I used staples of uniform composition and based the strength of my magnet on the number of staples it could pick up. I decided to use staples because they have magnetic attraction and allow for a relatively accurate comparison due to their light weight. I trailed each magnet and recorded the number of staples each magnet could lift, that is, the maximum number of staples.

TRAIL RESULTS

MAGNET #MASSNUMBER OF LAYERS OF COILSAPPROXIMATE NUMBER OF COILSMAXIMUM NUMBER OF STAPLES PICKED UPSTAPLE/MASS RATIO (X100)
150.0 grams0000
256.4 grams1~1501323.8
362.7 grams2~3002743.1
468.9 grams3~4504565.3

TRAIL SUMMARY

After performing several trials, it was evident that the more number of coils present, the stronger the magnet and hence, my hypothesis was correct. That is, there was an evident proportional linear relationship between the Number of Coils and the Strength of the Magnet. The third part of our assignment was to bring our strongest magnet to school for a practical assessment and compare it relatively to all the other magnets produced by fellow students in my class. I decided to use my 450 Coil Magnet as it was strongest of all three, did not exceed the 80 gram restriction on the mass of the magnet and gave the best staple/mass ratio.

PERFORMANCE RELATIVE TO OTHERS

Unlike my trail method, the strength of our magnet was tested differently at school. Instead of our magnet's direct contact lifting strength, the magnetic field strength of the electromagnet at a distance was tested. This was done by placing an iron object on a set of electronic scales, and determining how much that iron object was lifted. Each electromagnet was positioned approximately 6mm above the iron object and then connected to a 4V power supply. Once the power was turned on, a negative value on the scale showed (negative because it was the lifting strength) and was then recorded as a magnitude. To relatively compare each...