Science

Science Coursework: How does the number of coils on an

electromagnet affect its strength?

Aim: - To establish whether a variation in the number of coils will affect an electromagnet's strength.

Scientific Knowledge: -

An iron core wrapped in a series of coils of insulated wire and then connected to a battery, will enable the core to pick up paper clips. This is because the current emitted from the battery to the coils magnetises the nail. This is known as an electromagnet. The current passing through an electromagnet produces a magnetic field. Therefore, the more turns of the coil you have, the greater the magnetic field and the stronger the electromagnet. This will mean more paper clips being picked up by the nail. The strength of an electromagnet can also be altered by varying the current or voltage. The more induced voltage, the stronger the electromagnet. An alternative way to strengthen an electromagnet is to replace the core with a "soft" iron core.

Prediction: -

An increase in the number of coils applied to the iron nail will cause an increase in the number of paperclips being picked up. (a positive correlation between the two variables)

This prediction derived from the scientific knowledge above -

'Therefore, the more turns of the coil you have, the greater the magnetic field and the stronger the electromagnet.'

Apparatus: -

Iron nail (1)

Paperclips (several)

Power supply (1)

Coil (1)

Method: -

The method was relatively systematic. We first allocated various people amongst our group to collect different equipment such as the iron nail, paperclips, coil and power supply. Following that, we connected everything securely and wrapped the coil five times around the nail. We then switched on the power supply and set the voltage to 4V. We tested the number of paper clips the nail would pick up, each time turning the power supply off and winding the coil five more times consecutively.

Fair test procedures: -

In the investigation, we controlled three main variables to ensure that our results were as accurate as possible.-

1) The voltage

We sustained the voltage to 4V all the way throughout the investigation. This would make the test more fair.

2) Distance between each coil

We made sure that each coil was 1.5 centimetres apart so that the current would flow evenly along the nail. This would also mean that the power of the magnetic fields around the iron nail were equal - each part of the nail would have the same magnetism.

3) scales

For precision, we repeated the investigation again for comprehensive analysis and more accuracy.

Results: -

First Results

No. of coils No. of paperclips supported

5 4

10 11

15 16

20 19

25 26

30 42

35 36

Second Results

No. of coils No. of paperclips supported

5 4

10 9

15 13

20 18

25 25

30 31

35 35

We can infer from the positive correlation evident in this scatter graph that the number of coils is proportional to the number of paperclips attracted, thus, the number of coils is proportional to the strength of the electromagnet.

Analysis: -

In the first set of results, there was an abnormal fluctuation of the number of paperclips supported by the iron

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