# IB Energy Topics

/A tutorial sheet on topic 8.1 energy sources and 8.2 thermal transfer is given below.

- The intensity of the Sun's radiation at the Earth's orbit is I. If the Earth's albedo is 𝛼 determine the average intensity over the surface of the entire Earth. [I(1-𝛼)/4]
- An Earth-like planet is discovered orbiting a distant star at an average distance of 2.7x10
^{12}m. If the power of the star is 1.3x10^{28}W, calculate the surface temperature of the planet. Take the albedo and emissivity of the planet as 0.3 and 0.61 respectively. [163.7K] - The solar constant is 1361 Wm
^{-2}. The albedo of the Earth is 0.33 and its emissivity is 0.61. Determine the surface temperature of the Earth if the albedo increases by 10% and the emissivity decreases by 10%. [292.5K] - The solar constant is 1361 Wm
^{-2}at the Earth's distance from the Sun. At what distance from the centre of the Sun is the solar constant 15 Wm^{-2}? What planet is at this distance? [Saturn] - A lake full of water has an area of 5.1x10
^{6}m and a depth of 40 m. The base of the lake is 34 m above the turbine in a power station. Determine the greatest possible output power of the station if 1000 kg of water flows through it every second. [1.08x10^{14}W] - In a nuclear power station 7.64x10
^{19}fission reactions of U-235 occur per day. Each reaction releases 190 MeV of energy. Determine the specific energy and energy density of U-235. Assume that the sample is pure U-235 of density 19.1 gcm^{-3}and atomic mass 235.0439 u. [7.78x10^{13}Jkg^{-1}, 1.49x10^{18}Jm^{-3}] - In the previous question U-235 only occupies 3% by volume of the fuel rod which has a uniform density throughout. Determine the specific energy and energy density of the fuel rod.[2.33x10
^{12},4.46x10^{16}Jm^{-3}]