Water Wheel Generator
Where does the electricity in our homes come from? Discover the practical development of energy transfer by building a water wheel generator and model firsthand how electricity can be produced at a massive scale.
- Conservation of energy
- AC generators
Since antiquity, water wheels have been used as a large source of energy and are a great example of the law of conservation of energy. Water wheels are large rotating wheels with buckets that capture water as it flows over the wheel. The potential energy provided by the force of gravity is what causes water to flow downward in lakes, streams and rivers. This water initially collects in the buckets on one side of the water wheel and thus one side of the wheel is heavier and begins to turn. The buckets with water rotate downward and empty into the flowing body of water at the same time that buckets at the top are filled with water. The rotating wheel has now gained kinetic energy and will continue to rotate as long as water continues to flow. The axle of the wheel is of great use when attached to different tools that transfer the mechanical energy of the wheel into other types of useful work such as grinding grain into flour, hammering metal or powering an electric generator.
At the budding of the Industrial Revolution in the early 18th century, water wheels were the main source of industrial power. Great scientific progress in the realms of electricity and magnetism was made in the 19th century when Hans Christian Oersted (1777–1851) discovered that an electric current flowing through a wire would deflect a compass needle and connected the two disciplines into the singular topic known as electromagnetism. In 1831, Michael Farady (1791–1867) discovered that rotating a magnet within a coil of wire would induce a current in the coil. This is known as Faraday’s law—a changing magnetic field produces a voltage called electromotive force, or emf.
A mathematical description of Faraday’s law is as follows:
Emf is the electromotive force or voltage (V)
N is the number of turns in a coil of wire
ΔΦ is the change in magnetic flux
Δt is the change in time
Magnetic flux (Φ) is defined as the average magnetic field multiplied by the perpendicular area it penetrates. The equation is:
B is the strength of the magnetic field,
A is the perpendicular area.
Faraday was thus able to create the first simple AC generator. This was a monumental scientific and economic development since instead of creating batteries with expensive chemicals to produce current; current could now be produced continuously as long as the magnet or coil continued to rotate.
Water wheels were soon coupled with the simple AC motor to generate electricity. The axle of the wheel was attached to a magnet placed within a coil of wire to provide a source of electric current. The stronger the magnet, the more turns in the coil, and the faster the magnet is spun are all directly related to how much voltage the generator can produce. By the end of the 19th century, there were 200 hydroelectric power stations in the United States. Hydroelectric power plants are a source of renewable energy and continue to supply countries such as Norway, Paraguay and Brazil with 85% of their electricity.
The purpose of this activity is to gain an understanding of conservation of energy and the production of useful electric power by building a model hydroelectric generator. A water wheel will be built and used to drive a handmade AC motor that will cause a small red LED to flicker on and off.
Binder clip, medium size, 2
Cork, size #14
Dowel rods, wood, 2
Foam base, 14" x 5" x 1"
Magnet wire, 30 gauge, 200 feet
Map pins, 8
Neodymium magnets, 2
Soda bottle, 2-L, cut in half
Stopper, rubber, size #6
- What is magnetic flux?
- An AC generator outputs 1 volt when operating. What would be the effect on the voltage if the generator’s magnet was replaced with one twice as strong?
- What are sources of renewable energy?
Exercise caution working with neodymium magnets—they are very powerful, and will snap together easily. Wear gloves to protect your fingers during the preparation. The magnets are fragile and may shatter if dropped or if they hit another object too hard. Keep magnets away from electronic devices especially computers. Clean up all spills immediately. Wash hands thoroughly with soap and water before leaving the laboratory. Follow all laboratory safety guidelines.
Part A. Gear Mechanism
Part B. Water Wheel
- Obtain the gear set. Separate out all three gears and set aside. The smallest gear will not be used in the activity and may be saved for future use or discarded.
- Obtain the cork, iron nail, cut soda bottle, one wooden dowel rod, ruler and scissors.
- Using the iron nail, perforate the cork through its center so that the nail goes all the way through. Note: Take care to slowly push the nail through and attempt to make the hole in the centered as much as possible on both sides of the cork.
- Pull the nail out and obtain the wooden dowel rod. Carefully push the dowel rod through the hole in the cork until the cork is now at the center of the rod.
- Use the ruler and pair of scissors to cut two slits in the bottle separated by a distance that is only slightly wider than the diameter of the dowel rod and are about one cm deep (see Figure 1a).
- Create exactly the same set of cuts on the opposite side of the bottle opening (see Figure 1b).
- Cut out the plastic flaps you just created on opposite sides of the bottle and set the dowel rod with the cork in the slots created as seen in Figure 3c. Spin the dowel rod. Note: If the dowel rod does not fit into the slots or if it does not spin freely, increase the width of the slots.
- Remove the dowel rod from the plastic bottle and insert the large gear on one of the ends of the rod. The gear should easily slide onto the dowel rod.
- Place the dowel rod back into the slots on the bottle and obtain a glue gun, iron nail, the remaining smaller gear, cardboard tube, and black rubber stopper.
- Push the nail through the back of the smaller gear until the head of the nail is flush with the gear (see Figure 2).
- Use the hot glue gun to adhere the gear to the nail.
- Insert the tapered end of the rubber stopper into one end of the cardboard tube.
- Once the glue has dried, align the gear on the nail onto the top of the gear on the dowel rod, making sure that the teeth on both gears are completely meshed. Hold the nail parallel to the surface of the table when you do this (see Figure 3).
- Ensuring that the plastic bottle and cardboard tube are on a flat surface, bring the cardboard tube up to the nail (which should be parallel to the table) and mark where the point of the nail touches the cardboard tube (see Figure 3).
- At this point, half of your group will work on building the water wheel, while the other half will work on building the AC motor.
Part C. AC Motor
- Obtain six map pins, three pipets, a weighing dish, the pink foam base, two binder clips and scissors.
- Cut the stem off the pipets, leaving only the bulbs (see Figure 4).
- Cut the bulb in the half so that you are left with two scoop-shape sides (see Figure 5).
- Repeat steps 2–3 for the remaining two pipets.
- Use the map pins to pin the 6 blades separated evenly around the cork as seen in Figure 6.
- Using scissors, cut out a 2" x 3" rectangle from the front of the bottle (see Figure 7).
- Place the dowel rod with assembled water wheel (cork with pipet bulb blades) into the slots on top of the bottle and spin the wheel. Note: If the wheels don’t spin due to hitting the inside of the bottle make the opening on the front of the bottle, deeper so that the blades do not make contact.
- Make two cuts separated by 2" along the center of one of the edges of the weighing dish (see Figure 8).
- On the opposite side of the flap cut an inch deep opening into the weighing dish (see Figure 8).
- Bend the flap down and attach a large piece of duct tape along the length of the flap.
- Insert the flap onto the slot created on the front of the bottle and adhere the weighing dish to the front of the bottle (see Figure 9).
- Place the rod with the water wheel onto the slots and attach binder clips to the side of the bottle and just above the dowel rod. Make sure that the binder clip comes as close to the rod as possible without making contact. The binder clips will ensure the dowel rod stays in place once the wheel is operating (see Figure 9).
- Glue the bottom of the 2-L bottle to one of the sides of the foam base with the weighing dish protruding out as far as possible. Note: The bottom of the bottle should be glued near the edge of the base so that the weighing dish can protrude as far as possible (see Figure 10).
Part D. Combining Water Wheel and AC Generator
- Obtain the iron nail with the small gear glued to it, cardboard tube, magnet wire, two neodymium magnets, sandpaper, tape and the red LED.
- Push the tip of the nail through mark on the cardboard tube that was made in step 14 of Part A and drop the nail straight down. Poke a hole through the other side as well. Note: Ensure the nail is as perpendicular as possible to the cross-sectional opening of the cardboard tube before piercing the other side.
- Make a short (0.5 cm) diagonal cut at the top of the tube to hold the wire.
- Unwind a small length from the coil of magnet wire (about 10 cm), and hook it into the cut (see Figure 11).
- Wind the entire spool of wire around the tube. Be cautious not to pull too tightly, as the thin wire may snap. Note: The more coils, the easier it will be to light the LED.
- Once you have to about 10 cm of free magnet wire left, make another diagonal cut on the opening of the cardboard tube and secure it the wire in it.
- Use the sandpaper to remove the enameled coating on the two ends of the wire coiled around the generator.
- (Optional) Test the coil using the multimeter’s “continuity beeper” function to ensure you have a complete circuit. If the test indicates you do not have a complete circuit, remove more enamel from the ends of the wire.
- If necessary, widen each hole in the cardboard tube again by inserting the nail through one hole at a time and then wiggle the nail using circular motions until the nail can spin easily.
- Test the nail’s ability to spin by holding the cardboard tube steady and spinning the nail. The nail should spin easily, without much friction to slow it down. If not, repeat step 9. Leave the nail in its slots.
- Carefully detach the magnets from each other. Slowly bring one inside the generator, gripping it loosely so it will attach to the nail on its own. It should attach by the flat side (one if its poles).
- Turn the nail so that when looking down into the tube the magnet is on the underside of the nail. Holding the nail firmly in place, grasp the the other magnet firmly, and slowly and carefully bring it toward the nail. If opposite poles are facing each other, a pulling force will be felt. If a force of repulsion is felt, flip the magnet around. Gripping the nail and magnet firmly, bring the second magnet as close as possible before releasing it, allowing it to attach to the other side of the nail (see Figure 12).
- Wind each sanded end of the wire around the leads of the LED, ensuring that the two leads do not touch each other and tape the LED to the side of the cardboard tube (see Figure 13).
- Spin the nail with both hands. Increase the spinning speed until you see the LED flicker on and off (see Figure 13).
- Stand the AC generator stopper end down by the water wheel and bring the gear on the nail to the gear on the dowel rod.
- Mesh the gears together so that the small gear on the nail is meshed directly on the top of the large gear on the dowel rod.
- Insert two map pins on the cardboard tube so that the heads of the pins align exactly with the center of each gear (see Figure 14).
- Ensuring the gears are exactly aligned, insert the remaining free dowel rod vertically into the foam base so that it stands straight just behind the back of each gear (see Figure 14). The map pins in front of the gears and dowel rod behind the gears will ensure the gears remain meshed once the wheel is spinning.
- Spin the water wheel with your hand and ensure that the wheels remain meshed when spinning. Note: In order to keep the gears meshed, adjust the height of the cardboard tube as needed by adjusting how far into the tube the rubber stopper is inserted.
- Your water wheel generator is ready for use! Follow your instructor’s directions for testing the water wheel.