Electricity Unit 2.1 WJEC

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Unit 2.1
Define electric current? State its units.
The rate of flow of charge. It is measured in amps, where amps also equal Cs^-1.
(C/s)
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Give the symbol equation relating charge, current and time (including units).
I=Q/t
I=Amp=Cs^-1 (Coulomb per seconds)
Q=Coulomb=As (Amp seconds)
t=seconds
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What does 'e' represent in electricity? State its units.
e is the elementary charge. e= 1.6 x 10^-19
A proton has the charge +e
An electron has the charge -e
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What direction does convectional current travel?
A convectional current is the flow of a positive charge. It travels from positive to negative.
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What direction do electrons travel in a circuit?
Electrons travel from negative to positive.
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How is current measured in a circuit?
Current is measured with an ammeter in series with the component.
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What is meant by drift velocity?
The average velocity of the electrons.
It is average as they move in random directions due to collisions with ions.
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What equation is used to find drift velocity?
What does each letter mean? State their units.
I= nAve
I= Current (A)
n= Number density of charge carriers (m^-3)
A= Cross-sectional area of conductor (m^2)
v= mean drift velocity (ms^-1)
e= elementary charge (1.6 x 10^-19)
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You must be able to derive I=nAve
What equations are used in this derivation?
Distance = speed x time = Length = l = velocity x time = vt (simply l=vt)
Volume of a cylinder = Al
Current = I=Q/t
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Other cards in this set

Card 2

Front

Give the symbol equation relating charge, current and time (including units).

Back

I=Q/t
I=Amp=Cs^-1 (Coulomb per seconds)
Q=Coulomb=As (Amp seconds)
t=seconds

Card 3

Front

What does 'e' represent in electricity? State its units.

Back

Preview of the front of card 3

Card 4

Front

What direction does convectional current travel?

Back

Preview of the front of card 4

Card 5

Front

What direction do electrons travel in a circuit?

Back

Preview of the front of card 5
View more cards

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