The invisible and abstracted nature of electricity in simple circuits makes it hard for students to develop an accurate mental model. While the water analogy is often used, building a tangible water model with "knobs and dials" for students to manipulate is a fantastic aid for explicit teaching. Let me show you how to build one in a day from available resources.
Construction tips:
Drain
I used 25 mm conduit for the drain - it has to be a larger diameter than the feed in from the pump or it will not cope because the feed pipe is under pressure and the drain is gravity only (incidentally, that is why the water to your hand basin arrives in 12 mm pipe but the drain is a minimum of 32 mm, usually 40mm)
You can bend conduit using a hot air gun. Gently heat all round in the area to be bent (takes a few minutes) once it is soft you can bend wearing leather gloves. Allow to cool (it is a thermoplastic). The connection to the tank is a 25 mm conduit fitting - you need to cut your own soft rubber washer (ensure rubber washer is on the outside as shown. I found push-fit the parts together (no glue) if more than enough. Does not leak and easy to disassemble.
Pump
It needs to have a "head" of at least 600mm. This is the one that I used, but cheaper ones can be found online if you are patient. Note the pictured one says "suitable for 0.6m high water features - that is the "head", or max height it will pump water vertically.
Tubing
I chose the 13 mm PVC tubing. If left wet, it will go cloudy after a long while (also quite stiff). Dunking in near boiling water or warming gently with a heat gun / hair dryer will make it clear and soft again.
Fittings
Mostly the 13 mm "watering system' fittings. Tank connections are not "off the shelf", sadly and I wasted several hours walking the store to find a reasonable solution.
You can see the fittings that I used in the video, but I can't find them anymore (they used to be at that ubiquitous hardware store). The cheapest and most effective solution I can find (once my old supply runs out) is to use a "hose joiner" (about $2!.
You need to cut a rubber seal and the images show do that and how to use. It does not matter if your cutting is rough, the sides it seals against are not where you have cut. Flat sheet rubber is readily available in hardware stores - or find pre-made rubber seals (I could not find a cost-effective solution in my local hardware). BTW - I have had many students over the years doing the science projects and needing to connect a hose to a container. Forget silicone or anything like that -this is a universal and readily available solution!
What are that weird extra connection in the top tank?
Since it has a lid, you need an air-breather tube to ensure the pressure is gravity only. Sure, I should have just drilled a little hole in the lid... next time :)
Top Tank
I choose a polycarbonate one to ensure it is crystal clear for students. It is more brittle so to create the holes I recommend a hole-saw not a drill. A twist drill tends to catch, rip the container out of your hands and split it. Yes, this is experience speaking :)
Have fun creating yourself!
Or, if you want a pre-made kit your lab-tech could assemble, send me an email (roger@learningforge.com.au). If I get enough interest I'll work out the details and get back to you with a price and timeline, no obligation from you at all.
Comentários