ch14 notes - 14.2 The Cosmic Crucible Nuclear fission- the...

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Unformatted text preview: 14.2 The Cosmic Crucible Nuclear fission- the process of splitting a nucleus into two smaller nuclei -man made nuclear power plants rely on nuclear fission of uranium or plutonium Nuclear fusion-process of combing nuclei to make a nucleus with a greater number of protons or neutrons-sun turns hydrogen into helium through nuclear fusion Inside the core of the sun (15 million K) there are positively charged atomic nuclei and negatively charged electrons moving at very high speeds-at low speeds, electromagnetic repulsion prevents the collision of nuclei-at high speeds, nuclei come close enough for the strong force to bind them together Strong force- bonds protons and neutrons together in atomic nuclei High temperature is very important for nuclei to collide and fuse Hydrogen nuclei are individual protons; helium consists of 2 protons and 2 neutrons-hydrogen fusion reaction transforms 4 individual protons into a helium nucleus with 2 protons and 2 neutrons Proton-proton chain : sequence of steps in the sun that begin with collisions between individual protons (hydrogen nuclei) o Step 1 : two protons fuse to form a nucleus consisting of 1 proton and 1 neutron (which is the isotope of hydrogen called deuterium) Converts a proton into a neutron which reduces nuclear charge from +2 to +1 The positive charge is carried off by a positron (the antimatter version of an electron with a positive charge rather than a negative charge) Neutrino : subatomic particle with a very tiny mass is produced in step 1 The positron wont last long because it meets up with an electron, and creates 2 gamma ray photons through matter-antimatter annihilation) Step 1 must occur twice since it requires a total of 4 protons o Step 2 : many deuterium nuclei are present along with the protons and other nuclei step 2 occurs when one of these deuterium nuclei collides and fuses with a neutron, along with the production of a gamma ray photon step 2 also occurs twice o Step 3 : requires the addition of another neutron to the helium-3, making it a normal helium-4 Occurs through the collision of two heliu-3 nuclei Final result is a normal helium-4 nucleus and 2 protons o Neutrinos and positrons carry off the energy released in the reaction Fusion of hydrogen into helium generates energy because a helium nucleus has a mass less that the combined mass of 4 hydrogen nuclei Which means when the 4 hydrogen nuclei fuse into a helium nucleus, a little bit of mass disappears, which becomes energy according to E=mc2 About 98% of the energy is kinetic Solar energy production remains steady because the rate of nuclear fusion is very sensitive to temp....
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This note was uploaded on 04/08/2008 for the course PHYSICS 029 taught by Professor Bryce during the Spring '08 term at University of Iowa.

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ch14 notes - 14.2 The Cosmic Crucible Nuclear fission- the...

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