Environmental Engineering Reference
In-Depth Information
2. How much carbon-14 would be left after a set number of half-lives?
This type of question asks how much quantity would be left after a set number of half-lives.
Half-Life of Carbon-14
Half-Life SpentQuantity (g)Years
0
10,240
0
1
5,120
5,730
2
2,560
11,460
3
1,280
17,190
4
640
22,920
5
320
28,650
6
160
34,380
7
80
40,110
8
40
45,840
9
20
51,570
10
10
57,300
Hydroelectric Power
Dams are built to create reservoirs that capture water, which is then released at a controlled flow, producing
electricity as it flows over turbines. Hydroelectric power supplies approximately 12 percent of the power in the
United States.
One major advantage of dams is the controlling of downstream flooding by containing the water produced by
spring thaws and heavy storms. This is important because a population lives along rivers and streams that
flood. Controlling flooding prevents deaths, property destruction, and damage to crops used for human food or
animal feed. One disadvantage is the buildup of silt behind the dam. As silt builds up behind the dam, the dam
holds less water, making the dam less reliable as a reservoir for water. This could increase water shortages and
decrease the potential to produce hydroelectric power.
Hydroelectric power plants are similar to coal-fired power plants in that both turn a turbine, which then turns
the shaft of an electric generator, producing electricity. Coal-fired plants use steam to turn the blades of the tur-
bine, while hydroelectric plants use water to turn the turbine. The result is the production of electricity.
