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.
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).
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.
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.
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.
– 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!
– I made a video for students so they could try out soldering. The end goal here is for students to solder capacitors back to back. I want the students to do this because easily purchased large capacitors are polarized. If a student hooks up a polarized capacitor backwards, it can get fried. By soldering them back to back, we get a non-polar capacitor. The capacitance drops according to 1/Ct = 1/C + 1/C but this drop is ok. And, students enjoy learning a new hands-on skill.