Solar houses use a variety of energy storage devices to retain ...

[CORALGRILL2014]

Solar houses use a variety of energy storage devices to retain the heat absorbed during the day so that it can be released during the night.
 
  Suppose that you were to use a device of this kind to produce steam at 100C during the day, and then allow the steam to cool to 0C and freeze during the night. How many kilograms of water would be needed to store 20.0 kWh of energy in this way? The latent heat of vaporization of water is 22.6  105 J/kg, the latent heat of fusion of water is 33.5  104 J/kg, and the specific heat capacity of water is 4186 J/kg  K. A) 12.4 kg
  B) 23.9 kg
  C) 35.7 kg
  D) 42.6 kg
  E) 54.2 kg

Question 2

When current is flowing in an ordinary metal wire, the magnitude of the average velocity of the electrons is closest to
 
  A) 10 m/s.
  B) the speed of light.
  C) 1 mm/s.
  D) 1 km/s.
  E) 1 m/s.

[fraziera112]

Answer to Question 1

B

Answer to Question 2

C