Sample teacher and student dialog. Include reference to Maker Journal page and button to link to student maker journal page.
T: I am going to show you pictures of some old devices like TV, radio, music players, phones. Older electronics and new electronics share the same principles of running a power through a circuit to work. What are some differences you noticed between these old electronics and what you might see today at home or at school?
S: They’re old. They look much bigger. They run on different media. They weren’t digital.
T: [Accept all answers] Yes that’s all true. What I want to point out is that things you use today has evolved and changed. Someone mentioned that these older machines were bigger. What innovations might have lead to their smaller sizes now?
S: They don’t use tape anymore. They electronics inside might have changed. The tv uses flatter screens now. Newer stuff is made from new materials like plastics, so they are thinner.
T: That’s all true. Like I mentioned earlier, old and new electronics operate in almost the same way, by using electricity to power your device so it can do something. One of the main reasons why these devices have gotten smaller is because the circuit boards have gotten smaller. One huge reason for that is because of a breakthrough in the transistor. Who has a guess on what a transistor is, and what it does?
S: They act as a doorway for electricity to flow. They transition the electricity.
T: Let’s watch the first 4.5 minutes of this video to understand the impact of the transistor, and understand a bit on what it does. We’ll go indepth on how it works later. [Show video]
2. Demonstrate transistors as an On-Off switch (or a valve):
T: The video was a good introduction to how a transistor works, but I think we need a better example that we might be all used to. Let’s go outside, there’s a water spigot somewhere that will demonstrate this. But on the way there, can someone remind how many parts makes up a transistor?
S: Well, according to the picture you have up in the classroom, a transistor looks like a box with three legs. One leg is called the collector, the middle leg is called the base, and other leg is called the emitter.
T: Great. I have that exact picture printed here as well. We’re going to use the water spigot here as an example of how the transistor work. So in a transistor, electricity flows into the collector. In the water spigot, this pipe carrying water is the collector, water is flowing into it. But is the water coming out at the end of this hose?
T: Why? What is stopping it?
S: That knob right there is turned off, so the water can’t get through.
T: Exactly. This knob, is called a valve, and like any valve, it works by letting things through or not. So on your transistor, that middle leg is called the base, and it’s exactly like the valve or the knob. When the water isn’t flowing, the spigot is in the off position. When the base is in the off position, no electricity flows through. It is stopped. What will it take for me to get water to the hose?
S: You have to turn the knob.
T: Exactly, what will it take for the base of the transistor to be turned on? It takes a charge of electricity. Once the base is given a mild charge, it is turned on, and electricity is allowed to flow to the emitter. Again, the emitter in this example is what?
S: It’s the hose.
T: When water flows from the pipe, through the valve, and out the hose, what position do we call this?
S: It’s in the “on” position.
T: How does electricity flow in the transistor?
S: It goes from the collector, through the base, and out of the emitter.
3. Transistor As Amplifiers
T: It was also mentioned in the video, that a transistor works as an amplifier. Does anyone know what amplifying means?
S: It means that you can boost up the signals. It can change it.
T: Exactly. Lets use this water spigot still as an example. Water pressure in the pipe is always the same. What can I do to change how water is coming out of that hose?
S: You can put your thumb on it. You can turn the knob to full blast.
T: Exactly. did I do anything differently on the pipe (or the collector end)? But I can control how water flows by controlling the knob. The transistor works the same way. Electricity in the collector end is the same, but by controlling the base, we can shape how electricity comes out the emitter end.
3. Build a valve
T: Okay class, we talked a lot today about how a transistor like a valve. A valve is something that opens and closes and allows substances to be stopped or allow them to move. We’re going to do a mini design challenge. We’re going to use a balloon, this is our collector, electrons have been collected here. Our challenge is to build something that can let air (or electrons) to pass out of the balloon, and that can also stop air from passing through.
4. Build a Simple Circuit with a Transistor
T: Now lets get back to building circuits. I am going to give you a handout, on it, there’s a picture of a simple circuit. With your group, and using the materials we have in our kit, build the circuit on the picture. When you build it, use the handout to write down the steps you took to build it. Write it as if you can give those steps to someone and it can help them build it without the picture.
S: How will we know if the transistor works?
T: Once you are done, the transistor can be turned on with your finger. Don’t worry, it won’t shock you. But damping your finger a bit, you can put your finger between the contact point, and the current should through to your finger and charge the base. What happens when the base part of a transistor is given a charge?
S: It is turned on, and electricity is allowed to flow.
5. Connecting transistors to computing.
T: It was also mentioned in the video, that transistors play a huge role in modern computing and technology. We can find transistor on any circuit board, but where else do transistors exist?
S: They are in the CPU, that is in every single computer device.
T: That’s right, the video mentioned that transistors helped not just to shape electrical devices but also helped to shape the world with computing. By acting as millions of On-Off switches, it has increased computing power throughout the world, but why does a couple of On-Off switches allow for so many of things that things we enjoy like smartphones, and computers, and games, and satellite navigation.
S: It just does.
T: Understanding that something is either “On or Off” , or if it is “A or B”, or if it is “Yes or No” is very important, and you do it every day without knowing it. You judge the distance of cars before you cross the street, and your brain makes a decision is it safe? Yes or No. You try to make a basket, and before you shoot, your brain asks is it close enough to shoot? yes or no? Then it asks, can my shot be blocked? Yes or no? Asking yes or no question helps us find information in a very powerful way. Does anyone have an example of a yes or no game?
S: Yes, we have played “Guess who?”, and that’s a game where you answer with yes and no.
T: We’re going to play a game very similar to that. I am going to think of a place in my head and write it down, and you can ask me only yes and no questions, you have 20 questions to figure out the place.
S: Great. Let’s do it.
T: Now that we have played the game, let’s reflect on it. Why is being able to tell if something is yes or no, or on and off, so powerful?
S: When you learn that something is yes, it eliminates other things. Like if you know the place you were thinking of is in California, then we know it is not in New York, or any other place outside of California.
T: Class, we learned a lot today about the transistor. Let’s take 15 minutes, and create a collage. You can take do it the traditional way and find and draw pictures, or you can do it using a presentation software. But the point of the collage will be to summarized what we know about the transistor, what makes it up, how does it work, what are things that are in it. Be creative and have fun. We’ll do a share out after about your collage and what we learned about the transistor.