L31+Power+F10 - The Sun Lecture 31 FEEL THE POWER Energy...

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Lecture 31 FEEL THE POWER: Energy Sources Key Idea: The power we use in our daily lives comes at a cost. The Sun Composition: 92% hydrogen, 8% helium Mass: 2 x 10 30 kg (300,000 times Earth’s mass) Average density: 1.4 g/cm 3 (~1,000 times H 2 density @ STP) Density near the center: 150 g/cm 3 Temperature: 5800 K surface, 10 7 K center Luminosity: 4 x 10 26 J/s Source of energy is thermonuclear fusion Overall reaction: 4 1 H ! 4 He + ENERGY At 10 7 K, all atoms are fully ionized forming hot plasma. Nuclear Fusion Reaction 2 H + 3 H ! 4 He + neutron + 1.70 x 10 9 kJ/mol The energy released in this fusion reaction is the nuclear binding energy. Requires a temperature of 40,000,000 K to overcome the Coulomb barrier and ignite the reaction. Sizes Relative size of an atom and of its nucleus +6 Carbon atom R atom = ~ 0.1 nm R nucleus = ~ 3 fm
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Potential Energy (kJ/mol) R (nm) +1000 +500 +100 0 p + p + 0.1 1.0 p + p + Potential Energy vs Distance Two deuterium nuclei What is the potential energy at extremely small distances?
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