The power of moving water has been used for centuries to perform work such as grinding grain or operating sawmills. In some regions today, water power is used to produce electricity. Water turns blades in a turbine, the shaft of which spins a generator that produces electricity. By building and experimenting with their own waterwheels, students can learn how water works.
- Stiff cardboard (corrugated works well)
- 2 plastic milk jugs
- Round pencil or wooden dowel (about 1 cm in diameter)
- Water and large plastic tub or access to a sink
- Safety goggles
- Towels (just in case!)
1. Cut out a circle approximately 10 cm in diameter in the cardboard. Draw five lines, evenly spaced around the circle, from the edge toward the center. Cut in from the edge along these lines about 4 cm.
2. Poke a hole in the center of the circle and insert the pencil or dowel. (Note: This should be a tight fit.)
3. Cut the tops off the milk jugs, creating two open jug bottoms about 18 cm high. In the top edge of each, cut a small notch approximately 1.5 cm square. From the cut-off tops of the jugs, cut five rectangles about 4 x 6 cm in size.
4. Insert the plastic rectangles lengthwise into the slits in the cardboard circle. This is your waterwheel.
5. In the tub or sink, place the two jugs with the notches facing each and then place the ends of the dowel into the notches. The pencil or dowel should be horizontal (parallel to the base of the tub or sink). Pour some water (0.5 – 1 L) into the jugs to hold them steady.
6. Then pour water slowly over the wheel from a height of 10 cm. What happens? Have students experiment by pouring the water from different heights–for instance, 15 cm, 30 cm, and 50 cm. Does this affect the speed of the waterwheel? Perhaps students could graph their results.
5. Discuss with students why certain regions–the Pacific Northwest, for example–rely more on hydroelectricity than do others. (They feature large, powerful rivers.) What would be the advantage of building a large dam to produce hydroelectricity? (Water falling from a greater height produces more energy.)
Extension: Challenge students to set up a waterwheel that does work the way the windmill (pinwheel) does in the other activity (Blowin' in the Wind).