16. The rate of radiant energy reaching the earth's upper atmosphere from the sun is about 1.50 kw/m2. The distance from the earth to the sun is 1.50 x 104: m, and the radius of the sun is 6.96 x 10: m. . a) Calculate the rate of radiation energy per unit area of the solar surface b) If the sun radiates as an ideal black body, what is its surface temperature? 17. Thermos for liquid helium. A physicist uses a cylindrical metal can 0.250 m high and 0.090 m in diameter to store liquid helium at 4.22 K; at that temperature, the heat of vaporization of helium is 2.09 x 10* J/kg. The can is completely surrounded by walls that are maintained at the temperature of liquid nitrogen at 77.3 K, with a vacuum between the can and the walls. how much helium is lost by now? The emissivity of the metal can is 0.200. The only heat transfer between the can and the walls is by radiation. 18. Thermal expansion of an ideal gas. a) the pressure p, volume v, number of moles n and Kelvin temperature T of an ideal gas are related by the equation pV=nRT, where R is a constant. Show that the coefficient of volume expansion of an ideal gas is equal to the reciprocal of the Kelvin temperature, if the volume expansion of copper and air at a temperature of 20"C. Assume that air can be treated as an ideal gas and that the pressure is held constant. 19. An engineer is perfecting an electronic water heater that supplies hot water continuously. A test design is shown in Fig. 17.34. The water flows at a rate of 0.500 Kg/min, the inlet thermometer registers 18.0-C, the voltmeter reads 120 V, and the ammeter reads 15.0 A [which corresponds to an input power supply of (120V)x (15.0 A)=1800W ] a) when a stable state is finally reached, what does the outlet thermometer indicate? B) Why do we not need to consider the heat capacity mc of the apparatus itself