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# Magnetic door investigation (electromagnetism)

Assessment focuses: AF3, AF4, AF5

## Context

Pupils looked at new magnetic security doors that had been fitted at the school's entrance and discussed the science behind them. Working with the technology department, the class teacher arranged for some ‘fabricated doors’ to be produced for use in science investigations.

Pairs of pupils were asked to design an investigation into the technology used for magnetic doors. They discussed factors that affect security, including area of contact surfaces, number of coils and size of current. They developed their own methods for determining the level of security.

## Pupil's work

To measure the door security, Pupil G and her partner decided to use the maximum distance from the coil at which the door is noticeably attracted. When asked about this, Pupil G said, ‘It's easy to feel when the pull of the electromagnet begins.’

When I did the magnet experiment I noticed at the ends of the magnet the iron filings stood up on end this is because the magnetic fields are not 2D they are 3D and so many filings were attracted to the south and north pole.Electromagnetic Door Catch InvestigationAim- To Investigate the performance of an electromagnetic door catch. To do this I am going to investigate how changing the number of coils of wire affects the strength of the magnet (electromagnet)

PredictionI think that the greater the number of coils the stronger the electromagnet will be. I think this will happen because the size of the electric current increases with the number of coils and this makes a stronger magnet.DesignMy input variable is number of coils. My output variable is the strength of magnet. To make my experiment fair I will control all the other variables such as the voltage or the length of the resistance wire. I will also do the experiment three times for at least 5 different number of coils. This should reduce the effect of any little errors.ApparatusTo carry out my test I will use the following apparatus - metal bar, electrical wire coated in

plastic, Newton metre, volt metre, power pack, ammetre, model of door, clamp stand.Method1. Set up the electrical circuit, as I have drawn in the diagram with the nail head in place by a clamp.2. Set the power pack to a voltage on the advise of my teacher (This must be kept same all the way through my experiment)3. Rub the coloured electrical

wire four times around the metal rod and link into the circuit as shown in the diagram.4. Measure the strength of the electromagnet on the door using the Newton metre and record this in the results table.5. Repeat this three times for four, eight, twelve, sixteen and twenty coils turning the power off after each trial.A table depicts number of turns of coil and maximum distance to door in mm

Pupil G and her partner planned to take multiple readings both to produce averages and to improve the reliability of the data. They were only able to collect one set of data in the time available so they produced a graph from this.

Illustration of a line graph depicting the relationship between the distance to the door and turns of coils for an electromagnetic door catch. The X axis of the graph depicts number of coils turned and Y axis of the graph depicts maximu distance to the door in mm.