The Earth's Core Maintains a Temperature of

Q20: The major user of solar hot water

Q21: Solar power requires backup systems for<br>A)windy days<br>B)cold

Q22: Akron, Ohio, which averages 201 cloudy days

Q23: As a general rule, winter thermostat settings

Q24: Light bulbs are now rated in _

Q26: Light-emitting diode (LED) bulbs last _ times

Q27: Select the correct statement.<br>A)Both visible light and

Q28: Select the correct statement.<br>A)In the Northern Hemisphere,

Q29: The use of wind power was first

Q30: Conventional solar cells contain layers of<br>A)carbon<br>B)silicon<br>C)zinc<br>D)tin