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# Find out what factors affect the strength of an electromagnet.

Extracts from this document...

Introduction

Farzana Jalil 10N

29/06/2002

The Electromagnet

Aim: To find out what factors affect the strength of an electromagnet.

In 1831, an English scientist called Michael Faraday and Joseph Henry from USA both separately showed that moving a magnet through coils of wire would generate a current flowing through the wire. If this magnet was thrust into the coil of wires, current flows in one direction but if it was taken out, the direction of current is reversed. This is called electromagnet induction.

Electromagnets are solenoid (coil of wire) with a piece of iron inside. We say that this iron is ‘soft.’ This means that it changes easily between being magnetised and demagnetised. Electromagnets become a magnet with the use of electric current flowing through them. This means the ‘soft’ iron is ideal for electromagnets, as they are constantly turned on and off.

In contrast, steel is magnetically ‘hard’ so it is therefore suitable for permanent magnets. The material holds on to its magnetism, which means it will be hopeless as an electromagnet but ideal for what a permanent magnet needs.

The magnetic field around an electromagnet is similar to that around a bar magnet but this one can be made stronger.

Middle

The magnetic field of thismagnetized iron bar can be made much stronger than the solenoid on its own.

Increasing the current in the solenoid increases the magnetic field induced in the bar magnet--but only up to a certain point. This is called the saturation value. The strength of an electromagnet depends on the saturation value of the bar magnet. This is the factor I am interested in for my investigation.

Prediction: I think that if the current is increased, the strength of the electromagnet is increased. My objective in the investigation is to find a relationship between the increase in current and what happens to the increase of electromagnet strength. For example, I want to answer the question “Does the strength of the electromagnet double if the current is doubled?”

Before doing the experiment, I am thinking that the electromagnet strength will double if the current is doubled, in the same way the electromagnet strength will triple or halve if the current is tripled or halved. I think this because the size of the current is directly proportional to the strength of the electromagnet, meaning if one is changed, the other is changed in exactly the same way.

Plan:

Conclusion

" colspan="1" rowspan="1">

2.5

2.6

2.5

2.5

3.9

4.0

3.7

3.9

3.0

4.8

4.6

4.3

4.6

3.5

4.6

4.6

4.6

4.6

4.0

4.3

4.3

4.3

4.3

4.5

6.6

5.1

5.2

5.6

5.0

6.3

5.2

5.9

5.8

I repeated this twice and obtained the results shown below.

 Current Strength 1 Strength 2 Strength 3 Average Strength 4.0 5.8 5.9 5.4 5.7 4.0 5.5 5.6 5.5 5.4

I wasn’t satisfied with the first result as it was too big but was happy when I obtained a result of 5.4 the second time.

Analysis: My graph shows that as the current increased, so did the strength of the electromagnet. The graph shows a strong positive correlation as the points are very close to the line o best fit. The two variables are proportional to each other so as one increases, so does the other.

The graph also shows that as the current is doubled, the electromagnet strength also doubles. When the current was 1.5 amps, the electromagnet strength was around 2 volts. When doubles, the current is 3 amps and the strength of electromagnet is around 4 volts. This is because the two factors are strongly related. As I have already explained, increasing the size of the current increases the electromagnet strength and the graph supports this. It also supports what I said in my prediction about doubling and halving the measurements.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

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