Download Handout Topic 5, 10 New Charge Carrier Drift teacher

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Handout Charge Carrier Drift , Kirchhoff’s laws
Ideal and Non Ideal Meters
Charge Carrier Drift
1. Define charge density and drift speed:
Density - The number of charge carriers per 1 m3 of conductor.
Drift speed -How fast the charge carriers “ drift” through a certain length – volume of
1 m3 of conductor in in one sec.
Explain the following formula:
I = nAvq
Current = number of charge carriers x cross sectional area x velocity x charge
2. Example . Show basic work
3. Why is drift speed so slow? Use the comparison of Cu and Germanium to
answer the question.
It depends on charge carrier density. The higher number of charges per 1 m3 , the
higher the density and the faster the drift speed and , subsequently current , will be: I
α v . Cu is 109 times faster than the semiconductor Ge because of its higher charge
carrier density, as a matter of fact directly proportional at 109 times more dense.
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4. If drift speed is so slow why does a light turn on so fast?
Kirchhoff’s laws
Note : this is nothing new.
Kirchoff’ s First Law
You already know that the current going to a parallel circuit is equal to the current
coming out.
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Kirchoff’ s Second Law
You already know that the sum of the individual voltage drops in a circuit is equal to the
total voltage of the circuit.
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New term Potential Difference sink = PD sink = Voltage drop
Some Examples - Show Work
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Ideal and Non Ideal Meters:
Summarize the differences:
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