Question
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Answer
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By being more reliable and allowing for miniturisation, transistors replaced which device in electronic devices?
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Thermionic valves
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No two electrons in an atom can simultaneously occupy ___ ____ ______ _____.
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The same energy state
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What word descibes the free movement of electrons in a metal lattice?
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Delocalised
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Compared to the current, what direction do free electrons roughly travel in a conducting metal lattice?
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The opposite direction
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When an atom does not have a complete outer shell, it can form what kind of bonds with nearby atoms?
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Covalent Bonds
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Ionic Bonds
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A semiconductor's resistivity lies between that of an insulator and a conductor. As temperature rises in semiconductors, resistance _______.
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Decreases
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What is the highest band occupied by electrons called?
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The valence band
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In a conductor, what do the conduction and valence bands do?
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Overlap
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In an insulator, the valence band is full of electrons. Therefore the gap between the bands are _____.
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Large
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What are ionically bonded molecules?
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Insulators
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What did de Broglie proposed that electrons could also be considered as?
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Standing waves
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In semiconductors, what is the distance between the conduction and valence bands relative to insulators?
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Small
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Semiconductors have almost filled valence bands. What are the two most common pure semiconductors?
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Silicon
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Germanium
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As temperature increases, what does thermal energy allow electrons in the valence band to do?
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Cross the gap
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What do the electrons leave behind in the valence band?
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Positive hole
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What direction, relative to the conduction band's current, does this new positive current flow?
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The opposite direction
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What is the process of adding atoms with a different amount of valence electrons to a semiconductor?
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Doping
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Silicon and Germanium do not need ^ to be a semiconductor. They are known as pure semiconductors. What is another name for them?
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Intrinsic semiconductors
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Opposite of the above require the addition of dopant atoms. What are these semiconductors called?
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Extrinsic semiconductors
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What are the two most common dopant atoms? (one each for n-type and p-type)
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Phosphorus
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Boron
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What shape do groups of silicon atoms form in a diamond lattice structure?
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Tetrahedrons
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What were early diodes and transistors made from?
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Germanium
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