sci_phy
Nuclear Fission and Fusion
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
Free online summary and notes (ICSE Class 10 Hindi). Read it here, no PDF download needed.
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Physics · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
The products weigh slightly less than the starting nucleus; that missing mass is the mass defect. Because c squared is enormous, even a speck of mass gives a large energy.
Those new neutrons can split more nuclei, giving a chain reaction. Uncontrolled it is a bomb; controlled in a reactor it heats water to make steam.
A moderator slows the fast neutrons so U-235 can absorb them. The steady heat boils water, the steam turns a turbine and a generator makes electricity.
This powers the Sun. It needs millions of degrees so the positive nuclei can crash together against their repulsion, which is why fusion power on Earth is so hard.
Hard words & meanings
| nucleus | the dense central core of an atom made of protons and neutrons |
| fission | the splitting of a heavy nucleus into two lighter nuclei, releasing energy and neutrons |
| fusion | the joining of two light nuclei into a heavier one, releasing energy |
| mass defect | the small loss of mass in a nuclear reaction that becomes energy |
| chain reaction | a self-sustaining series of fissions where neutrons trigger further fissions |
| control rod | a boron or cadmium rod that absorbs neutrons to control a reactor |
| moderator | a material such as water or graphite that slows fast neutrons |
| isotope | atoms of an element with the same protons but different numbers of neutrons |
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