ElectromagnetsOctober 16th, 2009

What is an electromagnet?

• An electromagnet is a magnet that is made using electricity

• They are very useful as they can be turned on and off (whereas a normal magnet is permanent)

• The disadvantage to them is that they must be continuously supplied with energy

How do electromagnets work?• Wires carrying an electric current produce a

magnetic field around them• If the wire is coiled, the electromagnetic field

pattern is similar to that of a bar magnet

Three ways to make an electromagnet stronger:

1. Use a bigger current2. Put more turns of wire on the coil3. Use an iron core inside the coil

• Explain how each of the above makes an electromagnet stronger (level 6)

The Domain Theory of Magnetism

• Neighbouring particles inside a magnet are called domains

• Each domain acts like a very small magnet within the material

• Normally, the domains are arranged randomly, however, when we magnetise the material all the domains line up in the same direction

Practical Evaluation TTS 2 Page 250 (APP Assessment)

Level 6• Make valid comments on the quality of their dataLevel 5• Evaluate the effectiveness of their working

methods, making practical suggestions for improving them

Answer Questions 1, 2, 5, 6, 7, 8

Analysis and Evaluation (APP Assessment)

Level 6• Select and manipulate data and information and use

them to contribute to conclusions• Draw conclusions that are consistent with the

evidence they have collected and explain them using scientific knowledge and understanding

Level 5• Provide straightforward explanations for differences

in repeated observations or measurements• Draw valid conclusions that utilise more than one

piece of supporting evidence, including numerical data and line graphs

Current (Amps)

Number of Paperclips

Number of Paperclips

Number of Paperclips

Average Number of Paperclips

0.5 2 4 3 31.0 5 3 4 41.5 6 6 6 62.0 8 3 7 62.5 8 10 9 9

1. Identify the independent and dependent variables in this experiment (APP AF4 level 6)

2. Were the results of the experiment reliable? Explain. Also, were there any anomalous results? If so, circle it on your table of results. Can you explain what might have caused it? (APP AF5 level 5)

3. Draw a graph of the results (APP AF5 level 5)4. Identify the pattern of the graph using your

answers to question 1 (APP AF5 level 5)5. Explain the pattern you stated in question 3 (APP

AF5 level 6)