Lesson: Hydroelectric Power

Which of the following statements correctly describe the disadvantages of building a hydroelectric dam?

1. Flooding the valley behind the dam submerges the plant life growing there. The plant life dies, and as it rots underwater, it releases large quantities of methane and carbon dioxide. Both of these gases contribute to the greenhouse effect in the atmosphere.
2. Hydroelectric dams are slow to respond to changes in electricity demand.
3. Hydroelectric dams are expensive to build.
4. The running costs of a hydroelectric dam are high.
5. A large amount of concrete is used to build hydroelectric dams. The production of concrete produces a large amount of carbon dioxide that is released into the atmosphere, contributing to climate change.
6. Flooding the valley behind the dam can lead to the loss of habitat for some plant and animal species.

Which of the following statements correctly describe the advantages of building a hydroelectric dam?

1. Building a hydroelectric dam releases no carbon dioxide into the atmosphere.
2. Building a hydroelectric dam releases no methane into the atmosphere.
3. Hydroelectric dams can respond quickly to changes in energy demand.
4. Hydroelectric dams are very cheap to build.
5. The running costs of a hydroelectric dam are very low.

What type of electric current do the turbines in a hydroelectric dam produce?