Introduction
Hydroelectric power plants use the force of falling water to spin turbines and generate electricity. Water stored behind a dam has potential energy because of its height. As the water flows down, the energy is converted into kinetic energy, which drives the turbines. In this lab, you’ll explore how water height affects the flow rate, a key factor in energy generation.
Research Question
How does the water level in a container affect the flow rate of water exiting through a tube, similar to water flowing through a dam?
Hypothesis
If the water level decreases, then the flow rate will ______________________, because
________________________________________________________________________________________________________.
Procedure
- Get teacher instructions for setting up the water jug and tubing.
- Ensure that the water jug is full of water (full water level).
- Secure the water jug upside down so the tubing hangs straight down.
- Ensure that there are no leaks.
- Place the large collecting container directly under the tubing outlet.
- Remove the rubber stopper and start the stopwatch at the same time.
- Allow water to flow for exactly 10 seconds, then quickly replace the rubber stopper.
- Measure and record the volume of water collected using the beaker or graduated cylinder.
- Record the volume collected in the data table.
- Let air into the jug through the tubing (to prevent shrinking).
- Fill the jug again completely with water and repeat two more times (3 trials per water level).
- Next, fill the jug to ¾ full, and conduct three trials. Repeat for ½ full, and ¼ full.
- Record all values and calculate flow rate using the formula: Flow Rate = Volume (mL) ÷ Time (s)
- Find the average of the three flow rates recorded for each water level.
Data Tables
Full Water Level
| Trial | Water Level (L) | Time (s) | Volume Collected (ml) | Flow Rate (mL/s) |
| Average Flow Rate: | ||||
¾ Water Level
| Trial | Water Level (L) | Time (s) | Volume Collected (ml) | Flow Rate (mL/s) |
| Average Flow Rate: | ||||
½ Water Level
| Trial | Water Level (L) | Time (s) | Volume Collected (ml) | Flow Rate (mL/s) |
| Average Flow Rate: | ||||
¼ Water Level
| Trial | Water Level (L) | Time (s) | Volume Collected (ml) | Flow Rate (mL/s) |
| Average Flow Rate: | ||||
Graphing
Create a graph of flow rate (y-axis) vs. water height (x-axis). Use the averages for each water level for flow rate. Use your data to show how flow rate changes with water level. Label axes clearly and add a title.
Analysis and Conclusion Questions
- What trend did you observe between water height and flow rate?
- Did your results support your hypothesis? Explain.
- How does this model help explain how hydroelectric dams use gravity to generate energy?
- Why would engineers want to build tall dams or store large amounts of water?
- Were your results consistent across trials? What could explain any differences?
- What do you predict would happen if you changed the width or length of the tubing? How might this relate to pipe or turbine design in a real dam?