## Day 145 – Black Box Quiz

Science 9 – For the final assessment in the electricity unit, I constructed 4 “black boxes”that had batteries and 3-4 bulbs wired in a variety of ways.  The task for the students was to connect the batteries to turn on the circuit and then unscrew (and then re-screw) one bulb at a time to see what effect it had on the circuit. From this they would draw a schematic for the circuit.

The students really got into it!  A couple of the circuits were pretty easy but there was one in particular that was difficult for them. As a teacher, it was so nice to see them work so hard to figure it out.  Eventually students started sharing ideas a little bit. I guess in a strict sense, this would be a type of “cheating.”  However, they weren’t being deceptive about it, I was right there while it was happening. While we can say that an assessment is useful for figuring out where the kids are in their learning, assessment should also be a learning experience as much as possible. I couldn’t ask for anything more from the students and this assessment.

Finally, the kids pretty much all really liked it.  There were a couple of fist-pumps from students after they figured out a circuit and despite the difficulty level of the assessment, they really loved it. Challenges and tests can be liked, it’s all about finding that sweet spot for authenticity and being within a student’s capabilities (aka Vigotsky’s Zone of Proximal Development).

## Day 134 – Ohm’s Law

Science 9 – Students used the PhET DC Circuit Construction Kit to explore the relationship between voltage and current.  I had them use the simulator because it’s difficult to get good data using our ammeters and voltmeters.  I found that it was too easy for kids to make a mistake, and then they get data that doesn’t reveal any patterns.

Even though in grade 9 the kids are not especially great at deriving equations from a linear relationship, they are able to see a pattern and relationship using a data table, and can use words to describe this relationship.

For example, with the table below once they’ve collected data for current using different voltages, they will see that the voltage is always 100x the current.  From this, most kids decide to write something like “resistance times current is voltage”

Resistor Size = 100 Ohm
Current  Voltage

## Day 131 – Circuit Voting Peer Instruction

Science 9 – We did lots of Peer Instruction in class today, here are a few of the questions.  Students were able to make progress going from one question to the next, but as always is the case in my classes, it was difficult to get the kids to walk around the room and talk to people that were not their friends. At one point I had them walking around but they stayed in their groups…

## Day 129 – Measuring Voltage, Current

Science 9 – The students finally started to take measurements on current and voltage today. They were glad to be rid of the compasses!  Reminder for next year if I teach science 9: buy new liquid filled compasses are are sensitive but not so jittery.

Students did a good job of reading the different scales on the voltmeters and ammeters. Of course, no one in the world uses these types of ammeters and voltmeters, everyone has and uses a digital multimeter.  But that’s what you get with public ed in BC.  No money to buy suitable equipment.

## Day 127 – Circuit Analysis Tool

Science 9 – Here is a tool I showed the students to use for analyzing circuits. They color code wires in a circuit according to high (purple) and low (blue) pressure.  A wire has equal pressure at all points.  In order for a bulb to light, they know there must be a pressure difference across the bulb, because charges move from high pressure to low pressure.  Tracing and colour coding the wires lets the students see which bulbs have a pressure difference and which ones don’t. We then quickly checked the circuits in real life to see that they agreed.

Once a person gets more comfortable with looking at circuits and schematics, they can easily identify a short. However, this is a great bridge between what they they’re learning (pressure differences) and what they can do (predict bulbs lighting).

## Day 125 – Water Analogy

Science 9 – Sometimes I worry if the students are not seeing the forest through the trees by working through all of the lab ideas.  Today I gave the students this as part of some practice.  Without having to read about the water analogy for circuits, all students were able to do this correctly.  Ok, it’s not the most difficult thing in the world but it gives me confidence that they are learning something.

## Day 123 – Bulbs in Parallel

Science 9 – Students continued with their circuits. Today’s results were really surprising to everyone.  By adding another bulb in parallel, the bulbs didn’t go dimmer!  This was a shock to everyone.  I tried to help them to understand what was happening by using an analogy of blowing through one small straw vs blowing through three small straws at once.  Unfortunately I didn’t actually have the straws and many kids thought three small straws would be harder to blow through.

Note to self: have a box of stir stick straws in class next year.

## Day 121 – Bulbs in Series

Science 9 – Students looked at how adding more bulbs in series affects the current of the circuit.  They figured this out quite well.  They then were given a reading and a worksheet to apply their new knowledge.

We went through the reading quickly and I pointed out to the students the parts where they should focus their attention.  I think some type of homework/reading quiz may be needed in the future to ensure that students review their readings.

## Day 117 – Capacitors in Circuits

Science 9 – The above video is me going over a lab that the students had already performed.  Sometimes I go over them again quickly to make sure we all have the same consensus on what happened.

Using capacitors in high school science in BC generally is not done. However, we are using them not to learn about time variant current characteristics, but to analyze the nature of charges in a circuit.

The insulator in the capacitor breaks our original model of complete circuits. We get a working circuit, yet we know that charges aren’t crossing through the capacitor. As well, a discharging circuit will light a bulb, so charges can’t originate from the battery. In fact, as shown in the video we must be able to reason that charges are everywhere in the circuit because the compass rotates in all parts of the circuit no matter where the capacitor is.

There is a lot more to say about this topic, but that’s the general idea. These are great activities for the students because it challenges them to reason through logical inferences. Fantastic!