Dams are barriers that hold back water and often form reservoirs or lakes. Water stored behind dams holds potential energy. The reservoir water flows through a pipe called a penstock and into a machine called a turbine. A turbine has blades like a fan. The water pushes against the turbine blades that turn. The turbine spins around and is attached to a generator that produces electricity.

There are two types of hydraulic turbines-reaction and impulse. A wheel invented by Lester Pelton is the now used impulse turbine and works most efficiently when the head, the difference in height between the highest and lowest level of water, is at least 800 feet.

Build your own Pelton Wheel and explore how with it you can efficiently convert potential energy to kinetic energy.

CAUTION! This activity requires experience working with tools and the close supervision of an adult.

For Pelton Wheel:

aluminum can
gloves
utility shears
stapler
awl
small ball of clay
metal hanger

For Activity:

pressure pipe
garden Hose
water supply
masking tape

To make the wheel:

1. Cut 1" off the top of an aluminum can.

2. Cut straight from the top opening to within 1" of the lower shoulder of the ca.

3. Cut along the opposite side in the same manner.

4. Carefully cut the two "halves" in half to make four "blades".

5. Cut the four blades in half to make eight blades.

6. Fold each blade at a 45° angle. Staple them on the fold.

7. Crease the length of each blade in the opposite direction of the natural curve.

8. Punch a hole in the center of the bottom of the can with the awl. Punch a hole in the bottom of another aluminum can that has been cut to a 1" height.

9. Join the two pieces by placing one inside the other to complete the Pelton Wheel.

10. Place a straightened piece of metal hanger through the holes in the Pelton Wheel to hold during the activity.

Moving Wheel Activity:

1. Make predictions about which water holes on the pressure pipe will produce water that will move the wheel. Write a statement in the form of a hypothesis based on your predictions.

2. Working in groups, one student holds the pressure pipe upright.

3. Another student holds the wheel in front of a water hole on the pipe. (The other holes should be covered with masking tape).

4. Another student uses the garden hose to produce water coming out of the hole.

How does water pressure, affect the turning of the wheel? Which is best low or high pressure for creating energy?

How did the results compare with your hypothesis?

Construct another kind of water wheel using paper cups, masking tape, straws, straight pins, and pencils. The steps are as follows:

1. Tape two straws perpendicular to one another.

2. Securely tape paper cups underneath the end of each straw.

3. Press a straight pin through the point where the two straws cross and press the pin into the eraser of a pencil.

4. Place the wheel underneath a water source such as a drinking fountain.

5. Record observations.