Edexcel AS physics DC electricity unit 2 section 2

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Define current?
The rate of flow of charge
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What's the formula for charge?
Q=IT
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What is the drift velocity?
Average velocity of the electrons
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What is the actual speed of electrons?
10^6 ms^-1
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What's the equation concerning current and drift velocity?
I=nvqa
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What do n,v,q and a mean in the current/drift velocity equation?
n=number of charge carriers per metre cubed, v=drift velocity, q=charge per carrier, A=cross sectional area in metres cubed
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How many charge carriers are in a perfect insulator?
0
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What are charge carriers called in liquids and gases?
Ions
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Define potential difference using words?
Energy converted per unit charge moved
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What's the formula concerning voltage and charge?
V=W/Q
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What is one volt equal to?
1 JC^-1
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What happens if you put potential difference across an electric component?
Current will flow
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What's the formula for resistance?
R=V/I
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What 3 things determine resistance?
Length (longer=more difficult for current to flow), Area (wider=easier for current to flow), resistivity (structure of material)
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What are the units for resistivity?
Ohm meters
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What's the formula for resistivity?
RA/L
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What is Ohm's law?
Current through an ohmic conductor directly proportional to potential difference with constant temperature
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What's the I/V characteristic for a metallic conductor?
A straight line
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What's the effect of temperature on the resistance of a metal?
Resistance increases as temperature increases
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3 examples of semiconductors?
thermistors, ldr and diodes
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How does temp affect thermistor resistance?
Increased temp=decreased resistance
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How does light affect LDR resistance?
Light intensity increase=resistance decrease
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What is forward bias in a diode?
Direction current is allowed to flow
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What happens in reverse bias in a diode?
High resistance and tiny current
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What is power?
The rate of transfer of energy
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What is one watt equal to?
1 joule per second
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What's a formula concerning power and energy?
P=W/T
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What's the formula for power in electrical circuits?
P=IV
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How can we calculate energy when we know power?
W=power x time (in seconds)
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What causes internal resistance?
Batteries use chemical energy to make electrons move, this causes collisions
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What is emf?
Energy per coloumb
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What is terminal p.d?
Energy transferred when one coloumb flows through external resistance
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What are the 2 emf equations?
EMF=I(R+r) and EMF=terminal p.d + lost volts
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What is Kirchoffs first law?
total current entering junction=total current leaving it
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What is Kirchoffs second law?
Total emf= sum of all p.d's
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Other cards in this set

Card 2

Front

What's the formula for charge?

Q=IT

Card 3

Front

What is the drift velocity?

Card 4

Front

What is the actual speed of electrons?

Card 5

Front

What's the equation concerning current and drift velocity?