Energy is the ability to do work. Moving or falling water can be used to do work and can be a powerful source of energy.

Hundreds of years ago, wooden waterwheels were used to drive machinery in flourmills and factories. Steam engines replaced wooden waterwheels in the nineteenth century. Today, hydroelectric power plants use water to make electricity. "Hydro" means water. Dams, usually in the mountains, are built to hold river water forming a lake behind the dam called a reservoir.

This reservoir water flows through a pipe called a penstock and into a machine called a turbine. This electricity then can go over wires to your home, your school, Movie Theater, factories and businesses.

This reservoir water flows through a pipe called a penstock and into a machine called a Water pressure is critical to potential energy. Create your own dam to find out if increased water level means increased water pressure? Make your predictions and use a pressure pipe to find out the answer.

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

For the pressure pipe:

5' plastic sprinkler or PVC pipe (2" diameter)
2" end cap
pipe adhesive
measuring tape
drill with 1/8" bit
small rat tail file (optional)
scissors
masking tape
safety goggles
safety gloves

For the activity:

pressure pipe
modeling clay
garden hose
water supply
measuring tape
chart paper

Make the pressure pipe:

1.Coat 1" of one end of the 5" pipe with pipe adhesive. Twist the end cap onto the coated pipe, sealing it against water leaks.

2.Drill a hole in the side of the pipe, just above the cap. Drill holes at 30-cm increments from this hole to the top of the pipe. Be sure the holes are aligned. (To prevent the drill bit from slipping, cover spots to be drilled with a piece of masking tape.)

3.Clean the holes with a rat-tail file or by plunging the drill bit in and out of each hole. This will smooth the openings of the holes, allowing water to flow more smoothly.

Discussion:

1. Do you think increased water pressure will affect water flow? State your prediction in the form of a hypothesis. Tell what you are basing your prediction on. Why do you believe what you do?

2. Plug all the holes in the pressure pipe, except the top hole, with large lumps of clay.

3. Place the pipe on an elevated surface such as an outdoor table or step so water squirts freely from the hole.

4. Hold the pipe perpendicular to the ground while the hose fills the pipe with water. Maintain the level so water continually fills the pipe but does not bubble over the tops of your "dam."

5. Measure and chart the distance water is ejected from the hole.

6.Keeping the water flow from the hose constant, unplug the holes, one at a time. As you unplug each hole, measure the distance water is ejected. Chart the results.

Graph the information from the chart you created using the level of the hole as the x-axis and the distance water ejected as the y-axis. What distances would you predict water would eject from holes drilled at 105-cm and 165-cm?

Tell in a one page paper how what you learned about water pressure apply to how a hydroelectric dam works.