# EDEXCEL AS PHYSICS DC ELECTRIC+NATURE OF LIGHT

Describe a semiconductor?
Number of free electrons varies with temperature
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Describe free electrons?
Electrons that arent held around nuclei and can move
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Describe a metal in terms of free electrons?
High number of free electrons
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Define 1 amp?
1 coulomb passes in 1 second
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Whats the equation for charge?
Q=IT
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Describe drift velocity?
Velocity of electrons moving towards the positive terminal
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What happens to free electrons as they move round a circuit?
They lose energy
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What is the term for the voltage between 2 points?
Potential difference
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Define 1 volt?
1 joule transferred when 1 coloumb passes
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Whats the equation for electrical energy?
E=ITV
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What are 2 derived equations for power?
p+I^2R and P=v^2/R
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What is resistance?
Collision during movement of free electrons
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What happens to metals at higher temperatures?
Atoms vibrate more strongly and have more violent collisions causing more resistance
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Define 1 amp?
1A flows when 1V is applied
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What material obeys ohms law?
Metallic conductor at constant temperature
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Whats the formula for resistance and resistivity?
R=PL/A
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What is resistivity?
Resistance between 2 points on a 1m^3 specimen
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Whats the relationship between LDR and resistance?
high light=low resistance
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Whats the relationship between thermistor and resistance?
high temp=low resistance
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What is emf?
Voltage produced by a cell
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What is emf alternatively?
Maximum pd across terminals
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Whats the formula for emf?
E=IR+Ir
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What is quantum light theory?
Light sometimes behaves like waves and sometimes like particles
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What is work function?
Energy required to just release a photoelectron
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Whats the formula for kinetic energy?
energy-work function
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whats the formula for electron volts?
EV=1.6x10^-19J
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Whats the formula for efficiency?
Useful/total
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## Other cards in this set

### Card 2

#### Front

Describe free electrons?

#### Back

Electrons that arent held around nuclei and can move

### Card 3

#### Front

Describe a metal in terms of free electrons?

Define 1 amp?

### Card 5

#### Front

Whats the equation for charge?