# IB Energy Topics

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

1. 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]
2. An Earth-like planet is discovered orbiting a distant star at an average distance of 2.7x1012m. If the power of the star is 1.3x1028W, calculate the surface temperature of the planet. Take the albedo and emissivity of the planet as 0.3 and 0.61 respectively. [163.7K]
3. 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]
4. 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]
5. A lake full of water has an area of 5.1x106m 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. [1.08x1014 W]
6. In a nuclear power station 7.64x1019 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. [7.78x1013Jkg-1, 1.49x1018 Jm-3]
7. 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.[2.33x1012,4.46x1016Jm-3]
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