Electromagnetic induction

Electricity or Magnetism?

Objective

Students will be able to demonstrate that electricity can be transformed into magnetic effects

Preamble

To have a successful activity, students will need to use good batteries. It is worth using new ones. The first activity is very directed for an inquiry lesson. I have found that the students find this so amazing and so unlikely, that they cannot possibly work it out for themselves.I have never tried telling the students to find out how they could use electricity to make a magnet from their textbook or the internet and then letting them try it. It doesn't seem to me that would give as much impact as just trying it directly from instructions. I have done it just as a demonstration and moved directly from there to the questions. That has worked well because the change from electrical energy to magnetic energy acts as a discrepant event. I have always used paper clips to show the magnetism. It is also possible to use iron filings but this gets messy.

Activity

Making a magnet

Equipment

Each group is given:

• 1 long nail or bolt
• 3 wires with crocodile clips
• 1 or 2 D batteries in holders
• One longer strip (about 50cm) of insulated electrical wiring with the ends stripped to expose the wires
• paper clips

Procedure

1. wind the long piece of wire around the nail at least 20 times leaving about 10 cm of wire hanging off both ends
2. Attach the wire to the batteries (or battery) using the wires with crocodile clips
3. Carefully holding the nail by one end, hold the other end close to some paper clips.
4. How many paper clips can you pick up?
5. What has the iron nail become?
6. Gently pull the nail out of the wire and hold it to the paper clips
7. How many paper clips will it pick up now?

basic circuit

Activity

Find out for yourself!

Ask a Question

1. Looking at the electromagnet,have the students think of some questions they could ask to find out more about how electromagnetic induction works.
2. Write all the questions the students think of on chart paper
3. Have the students select the question they would most like to try to design an experiment to answer.
4. The students write down their question and then a procedure for the experiment they are going to perform to answer the question. I always insist they include the chart or table they will use for the results.
5. Check the procedure for each group to ensure the experiment is valid.
6. Give the students the equipment they need and allow them to perform their experiments, write down the results, and answer question.
7. Allow each group time to share their results with the class.

Reflection

Some considerations to ensure a successful class

• If your students have never generated their own questions to study in this way, use them to complete a "formula" style question such as "What would happen if I changed ..............?"
• If you have a couple of students simply cannot think of a question, and no-one else has come up with the idea already, suggest they switch the experiment they just did. That is, they used electricity to produce a magnet. Can they use a magnet to produce electricity. This is very useful as a start for the next lesson. The students must be reasonably competent for this though.
• Interfere with the groups that form only if absolutely necessary. If possible, split a group into two rather than insist a student changes question.
• Writing a procedure is very difficult for students. I allow the first step to be "Set up the circuit shown in the diagram". After that it is easier.
• Question the students carefully on what it is they are going to measure and how they intend measuring it. Most of my students fairly quickly come up with what they are going to measure - usually which is the better magnet. But before they can really write a procedure, they must also know how they intend to measure the strength of the magnet. Once they have these two questions carefully answered in their heads, the procedure for their experiment is clearer.
• Getting the experiments done always takes time.
• Offering the students the possibility of using a powerpoint presentation for sharing their results with the class has resulted in greatly improved presentations and greatly improved participation by the rest of the class in discussing and learning from each group's results.

Assessment

Assessment

Assess the students on the written work produced, looking for a clear question, an understandable procedure, clear presentation of the results and a thoughtful conclusion.

I also write a couple of comments about the quality of the oral presentation and the team work and enthusiasm shown.

I do not grade the question itself as that would indicate to a student, not the quality of their work or learning, but whether their personal interests have value or not.

Self Assessment

Self Assessment/Reflection

This activity lends itself well to a self-assessment or self-reflection. You could ask the students to reflect on:

• How well they think the experiment they designed answered the question they asked
• How well they think their group worked together
• What they would need to do to build a stronger electromagnet
• What they were disappointed in with their experiment. It is here that students often have told me that they were disappointed in the question they asked and they wished they had asked something better. Great learning!
• What they would do differently if they had to do this again.

Some sample questions asked by the students

• Is it better to have more coils or less coils?
• Does it work better with more batteries?
• Does it work better using uninsulated wire?
• Does it work better if the coils are close together or further apart?
• Does it work better if there are two wires attached to the coiled wire and the negative side of the battery?

(In case you are wondering about this question, yes it does, in my classroom anyway. Anyone know why?)

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