Posting Seven -- Series and Parallel Circuits

One of the hardest concepts for students in the grade nine applied science course to fully understand is the parallel electrical circuit. I have tried many different approaches to teaching the parallel circuit over the years but it appears that the learners are not yet ready for this concept. This year I took an inquiry-based learning approach and the results were more successful than in the past.

1. Initiate and Plan – ENGAGE

We began our study of electrical circuits with the series circuit. This allowed us to become familiar with the parts of the circuit (load, source, conductors, and switch) and trouble shoot problems that are commonly encountered when connecting the circuit.

Once the class could build a simple series circuit I taught them the symbols used to record their circuits. You can read more about this process in the previous blog entry (posting six). It is also an excellent example of how the conclusion of one inquiry becomes the initial planning stages of the next inquiry.

As an introduction to the parallel circuit, we watched a video wherein both the series and parallel circuits where examined and explained using age appropriate language and examples. Then we watched a simple power point presentation that I created that covered the same ground. Then we took notes, in the form of a t-chart, to compare the two types of circuits. Next, we did a set of questions together, step by step, that covered series and parallel circuits. Finally, for our exit card that day I distributed small recipe cards. The students were instructed to use the appropriate symbols to draw a series circuit on one side of the card and a parallel circuit on the other side of the card. They were allowed to use their note books, text books, confer with each other and check with the teacher during this process (diagnostic or “assessment for learning”).

2. Perform and Record -- EXPLORE

Prior to the next class I went through each of the cards. Using two sets of stickers – big stars and little stars—I assigned groups and which parallel circuit would be built. I used colour coded big stars to determine which students would work together in small groups, students with the same colour big stars would be in the same group. I used smaller stars to determine which parallel circuit I would require them to build –the circuit drawing with the small gold star would be built. In this manner, everyone go two stars—because they are all stars -- yet I got to mix the groups up and control what circuit would be created. The students responded amazing well to this sticker system and seemed quite pleased that I had made at least some of the decisions for them!

It is not uncommon to have some students absent everyday in applied classes at our school. For those students who were missing on the day we made our cards I took a blank card for each of them, wrote the absent student’s name on it and put two star stickers on the blank card – one large one to determine the group the student would be in and one small one, that was any colour except gold!

The next day the cards on which series and parallel circuits had been designed were returned to the students along with the instructions to move into their assigned groups, pick up all the equipment they needed to build the circuit drawing with the gold star on it and go to it!

The students were soon demonstrating their ability to read circuit diagrams, planning what equipment they needed to build their circuits, constructing circuits, using instruments (voltmeters and ammeters), and experimenting to see if they could successfully complete the task.

3. Analyze and Interpret = EXPLAIN

As stated previously, building parallel circuits is very challenging for students in the grade nine applied science class so it was not surprising to me that this task took a lot of time and patience on behalf of the students. While trying to succeed they engaged in constant analyzing, evaluating and reviewing in numerous attempts to get their circuits working. Of the four groups one group finished much sooner than any of the other three. At that stage I dispersed the members of the successful group amongst the other three groups to be their “consultants”.

It was interesting for me to observe many group members using the voltmeters to determine that there was in fact current running through the parallel branches even though the light bulbs were not coming on.

4. Communicate = EXTEND

Now the students took the initiative to test all the light bulbs in their circuits and replace the ones that were not functioning. They even wanted to know the proper way to dispose of the burnt out bulbs!

This weekend I am working on my midterm report cards marks. This class has a mean score of 82%. Now I am worried that my administration will be questioning why my marks are so high! If they do, I shall refer them to this blog!

Here are some videos showing the levels of engagement in the students during this inquiry!

Posting six -- Current Electricity -- The Electrical Circuit

Today my grade nine applied science class performed an open ended lab on electrical circuits. We started by drawing a simple T-chart to list the symbols for the basic parts of a circuit (battery, wire, open and closed switch, light bulb, etc). We talked about how these symbols could be used by electricians anywhere to wire up a building, it didn’t matter what language they spoke the symbols would be the same.

1. Initiate and Plan = ENGAGE

I drew a super simple circuit diagram, using symbols, on the board and told the students to work in small collaborative groups build it.

I did not distribute any materials. I showed the students where all the materials were, in containers, on the side counter and told them to get what they needed. At first the students questioned how they were supposed to know what materials they needed. I simply told them to refer to their t-charts to decide what they should take from the bins. It took them about 20 seconds to figure it out!

The students investigated how to build the circuit and called me over to show me when the light bulb came on.

My second instruction to the students was to “construct at least four more working circuits and use the symbols to draw them”. Questions that were quickly asked, and answered, by the class included:

“How will we know if the circuits work?” “The light bulb will come on.”

“If we include a switch in our circuit should we draws it with the switch open or closed?” “Draw it both ways and then we will have two circuits done already!”

“What if the battery is dead?” “Then the light bulb won’t come on.”

“”How we will know if we blow the bulb?” “We will hear and see it pop.”

Really, the students did not need me. Together they had enough knowledge to perform the task perfectly. So I gave them some “special pink paper” to draw their circuits on and let them go to it.

2. Perform and Record = EXPLORE

The students designed a number of circuits. Interestingly, they were all series circuits. I thought that given enough time some might move onto parallel circuits. They enjoyed constructing the circuits and experimenting with various combinations of electrical equipment.

Safety note: The source of electricity was D cell batteries (1.5 volts, when new) and each group was limited to three of them so there was no danger of electric shock.

3. Analyze and Interpret = EXPLAIN

Although some of the students used the symbols correctly right from the start, to record their circuits, other students insisted on making artistic renditions of their circuits when instructed to draw them. When asked why they didn’t just use the symbols which were so much quicker and easier they replied “but I really like art.”

Others didn’t want to draw anything at all but when they realized how quickly they could sketch the symbols they decided it was easier to comply than to waste time arguing.

A few used the symbols correctly but drew their circuits as a straight line. When it was pointed out to them how the circuit actually went around in a continuous loop they quickly recognized the error of their ways and were pleased that it could quickly be corrected by drawing a wire from the end of the line around to the beginning rather than starting over from scratch.

4. Communicate = EXTEND

Once all the groups had built and drawn four circuits we discussed the problem of how to decide if it was the battery or the light bulb that was defective when a circuit was built correctly but didn’t work. This is when I introduced the voltmeter.

Without further instructions the class rushed to collect all the batteries out of the container and test them using the voltmeters (using instruments). This led to them discovering what to do if the voltmeter needle went in the wrong direction and what scale to choose on the voltmeter. Indeed five dead batteries were removed from the collection. When the students observed that I was asking them to give me the dead batteries and that I was placing them in a clean plastic jar rather than throwing them into the garbage they questioned me about this practise. This lead to some reflecting and explaining regarding the correct disposal of batteries and what would happen if they went to the landfill.

Once we had all decided that all the batteries were functional it was a natural progression to then test all the light bulbs. The next teacher to use our equipment will be very pleased – everything is fully functional and all the trouble shooting has been done for her!

How will I evaluate today’s lab? I collected the pink papers that the students had drawn their circuits on. This has provided me with documentation on their learning process.

Static Electricity – Creating an Electrostatic Series -- Posting five

I have been re-energized by attending a Smarter Science symposium over the weekend so today I facilitated an inquiry-based collaborative learning experience into electrostatic series with my grade nine applied class.

1. 1. Initiate and plan – ENGAGE

I began the class by modeling how a balloon holding static charge can be used to pick up pieces of confetti (the holes collected out of my hole-puncher). We drew on our previous knowledge, from last week’s classes, to determine how the balloon could be charged with static electricity.

I told the students that we were going to do an investigation to determine what material would produce the greatest static charge on the balloon. In the middle of the sun burst diagram we wrote: “What type of material will make the most static electricity?” This was our dependent variable.

We used the sun burst diagram to list all the different things that could observed while doing a lab.

These were:

1. The time spent rubbing

2. The type of rubbing

3. The shape of the balloon

4. The size of the balloon

5. The colour of the balloon

These items were listed on to little post it notes and stuck around the rays of the sun burst diagram.

We moved to page two of the sun burst diagram, to the Initiate and plan page, which has a picture of the brain and says “brainstorming” on in. Here we decided how we would control the variables that we had listed on our post it notes. This could have been done group-by-group but I chose to do it as a large group activity so everyone would be controlling variable in the same manner. Several excellent suggestions were made so we voted to decide which ones to go with. For example, the amount of time spent rubbing could have been 30 seconds, 60 seconds, 90 seconds, etc. All were good choices so I narrowed it down to the first four suggestions and we voted, by a show of hands. Thus, the controls were determined to be:

1. Time rubbing = 1.5 minutes

2. Type of rubbing = circular motion

3. Size of balloon = full capacity

4. Colour = orange (that’s what I had the most of)

5. Shape of balloon = oval

Now we moved all of our post it notes over to the fish bone diagram where they were taped down. I had actually forgotten that we should tape them down at this point but the kids quickly reminded me.

2. Perform and Record = EXPLORE

The students designed an observation table by drawing a simple t-chart. On the left side they wrote “type of material” and on the right side they wrote ‘number of pieces of confetti collected”. Working in pairs they performed the investigation and were incredibly intr4igued by it. It made me realize how much of the sense of wonder grade nine students still have in them.

Some of the comments I heard during the lab were:

“I can hear the static electricity!”

“Listen!”

“You can hear it crackling!”

“Don’t forget to discharge between tests.”

“Make sure you rub in little circles.”

“It’s your turn to time while I rub.”

“Let’s split the amount of confetti pieces we have to count and each count half of them then add our two answers together.”

3. Analyze and Interpret = EXPLAIN

After testing a variety of materials, such as wool, silk, hair, fur and plastic the students were able to analyze their data to determine which materials created the most static and which created the least. At this stage I introduced them to the concept of “Electrostatic Series” with a very simple definition of “ a list of materials from the most static to the least static”.

4. Communicate = EXTEND

Each student created an electrostatic series by listing the materials they tested, in order, from those that created a static charge to those that created the least. They were able to quantify their results because they had counted the number of pieces of confetti that was attracted to the balloon during each test.