I will begin today's session by asking the students, now that they have experimented in several lessons, if they think the number of wire coils will affect the strength of the magnet?
My students had differing opinions, which they supported with evidence. As you watch the following clips, listen of the 3 leading ideas. Some students thought more coiling would cause the magnet to be weaker, as the electricity would have to travel in too many circles. Another group thought the magenta would be stronger with more winds, because the electrons would be closer together, while a third student thought it wouldn't matter because the electricity has to flow through the same amount of wire, regardless of it's arrangement.
I explain to the students that today they will build their electromagnet again and have 5 minutes to test it. Then, they will begin to gather data to answer our focus question, "Does the number of winds affect the number of washers picked up by your electromagnet?"
I will have every group test, 3 times, 10, 20, 30, 40, and a choice number of winds. They will gather the data on a table in their science notebooks and then create a graph of the final results.
As a class, we decided to use the highest number in each of the categories, after 3 tests.
In staying with our routine, while the students self-direct their work, I circulate and ask questions while watching for safety and precision. This group was predicting their outcomes and stating theories, based on data they have already gathered.
When I approached this group, they were testing 30 winds three times for accuracy. My sound blanked out, but I asked them why they thought the number of washers increased and what they predicted for their results with 40 wraps of the wire. They guessed that they would go up 3 or 5 ecause that is what happened between 10-20 winds (5 more) and 20-30 winds (3 more).
To close the session, I asked students to describe what they found out and answer the focus question. This partnership (no sound, but you can see by their hand movements), were able to explain to me that the greater number of wire wraps, the stronger the magnetic force. I asked what they would think about 100 winds. They laughed and said they didn't want to wrap that many times, but that it would probably pick up all of the washers!