Carrier Density
The number of free charges per cubic metre
Mean Drift Velocity
The average displacement per unit time of charge carriers travelling along a wire
Compare Drift Speeds with Electricity
Drift Speeds = very slow
Electricity = instantaneous
Electron Drift: Normal Temperature
- electrons hurtle around continuously
- collide with ions
- no net energy transfer (due to random movement)
- therefore no current
Electron Drift: When Voltage is Applied
- electron accelerated from -ve to +ve
- movement is superimposed on top of random velocities
- responsible for electrical effects
Conductors
- n
- increasing temp (4)
Large value for n
Increasing the temperature:
- increases vibrations of the ions
- increases resistivity
- decreases current
- decreases drift speed
Insulators
- n
n is near to 0
Semiconductors
- n
- increasing temp (2)
n about a million times smaller than conductors
Increasing the temperature:
- increases carrier density
- decreases resistivity (thermistor)
Conduction Electrons travel …
faster in semiconductors than in conductors (as n is low)
You can alter n (carrier density) by
Adding impurities (doping)
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GCSE Equations - All34
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Module 1 - 1.1.1 Planning2
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Module 1 - 1.1.2 Implementing1
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Module 1 - 1.1.3 Analysing3
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Module 1 - 1.1.4 Evaluation1
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Module 2 - 2.1.1 Physical Quantities2
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Module 2 - 2.1.2 SI Units9
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Module 2 - 2.2.1 Measurements and Uncertainties9
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Module 2 - 2.3.1 Nature of Quantities2
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Module 3 - 3.1.1 Kinematics7
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Module 3 - 3.1.2 Linear Motion7
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Module 3 - 3.1.3 Projectile Motion1
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Module 3 - 3.2.1 Dynamics6
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Module 3 - 3.2.2 Motion with Non-Uniform Acceleration3
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Module 3 - 3.2.3 Equilibrium10
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Module 3 - 3.2.4 Density and Pressure6
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Module 3 - 3.3.1 Work and Conservation of Energy5
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Module 3 - 3.3.2 Kinetic and Potential Energies1
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Module 3 - 3.3.3 Power1
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Module 3 - 3.4.1 Springs11
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Module 3 - 3.4.2 Mechanical Properties of Matter11
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Module 3 - 3.5.1 Newton's Laws of Motion6
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Module 3 - 3.5.2 Collisions4
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Module 4 - 4.1.1 Charge7
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Module 4 - 4.1.2 Mean Drift Velocity10
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Module 4 - 4.2.2 E.m.f. and P.d.8
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Module 4 - 4.2.3 Resistance6
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Module 4 - 4.2.4 Resistivity6
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Module 4 - 4.2.5 Power3
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Module 4 - 4.3.1 Series and Parallel Circuits2
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Module 4 - 4.3.2 Internal Resistance6
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Module 4 - 4.3.3. Potential Dividers1
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Module 4 - 4.4.1 Wave Motion20
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Module 4 - 4.4.2 Electromagnetic Waves11
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Module 4 - 4.4.3 Superposition9
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Module 4 - 4.4.4 Stationary Waves8
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Module 4 - 4.5.1 Photons3
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Module 4 - 4.5.2 The Photoelectric Effect8
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Module 4 - 4.5.3 Wave-Particle Duality1
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Mock Revision - ignore49
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Astrophysics - ignore37
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Module 5 - 5.1.1 Temperature9
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Module 5 - 5.1.2 Solid, Liquid and Gas14
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Module 5 - 5.1.3 Thermal Properties of Materials3
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Module 5 - 5.1.4 Ideal Gases11
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Module 5 - 5.2.1 Kinematics of Circular Motion3
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Module 5 - 5.2.2 Centripetal Force7
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Module 5 - 5.3.1 Simple Harmonic Oscillations6
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Module 5 - 5.3.2 Energy of a Simple Harmonic Oscillator2
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Module 5 - 5.3.3 Damping14
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Module 5 - 5.4.1 Point and Spherical Masses5
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Module 5 - 5.4.2 Newton's Law of Gravitation1
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Module 5 - 5.4.3 Planetary Motion5
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Module 5 - 5.4.4 Gravitational Potential and Energy9
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Module 5 - 5.5.1 Stars24
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Module 5 - 5.5.2 Electromagnetic Radiation From Stars30
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Module 5 - 5.5.3 Cosmology31
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Module 5 - Detailed Sections of Astrophysics17
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Module 6 - 6.1.1 Capacitors9
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Module 6 - 6.1.2 Energy5
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Module 6 - 6.1.3 Charging and Discharging Capacitors9
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Module 6 - 6.2.1 Point Spherical Charges4
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Module 6 - 6.2.2 Coulomb's Law4
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Module 6 - 6.2.3 Uniform Electric Field2
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Module 6 - 6.2.4 Electrical Potential and Energy8
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Module 6 - 6.3.1 Magnetic Fields16
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Module 6 - 6.3.2 Motion Of Charged Particles8
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Module 6 - 6.3.3 Electromagnetism19
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Module 6 - 6.4.1 The Nuclear Atom12
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Module 6 - 6.4.2 Fundamental Particles14
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Module 6 - 6.4.3 Radioactivity17
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Module 6 - 6.4.4 Nuclear Fission and Fusion15
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Module 6 - 6.5.1 Using X-Rays13
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Module 6 - 6.5.2 Diagnostic Methods in Medicine8
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Module 6 - 6.5.3 Using Ultrasound18
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Module 3 Practicals8
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Module 4 Practicals15
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Module 5 Practicals10
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Module 6 Practicals9
