Electrics

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What is current?
The rate of flow of charge
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What is the equation for Current involving charge and time?
Q=IT
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What is a coulomb?
Amount of charge that passes in one second when the current is 1 amp.
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What is drift velocity?
the average velocity of the electrons, slowly moving towards the opposite charge.
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What is the equation for Drift velocity?
I=nAvq
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What does the 'n' stand for in the I=nAvq equation?
Number of charge carriers
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What does the 'q' stand for in the I=nAvq equation?
Charge carried by each charge carrier.
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What are the charge carriers in a metal?
Free electrons.
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Do semi conductors have more or fewer charge carriers than metals?
Fewer charge carriers
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What are the charge carriers in molton ionic crystals and ionic solutions?
Positive and Negative ions.
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What is potential difference?
Evergy converted per unit charge moved.
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Whats the equation for PD involving Energy and charge?
P.D=W/Q
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What is resistance?
Resistance= Voltage/current
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What three factors determine resistance?
Length, area and resistivty
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Give two environmental factors that effect resistance
Light and temperature.
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What is ohms law?
If the temperature is constant, the current though a ohmic conductor is directly proportional to the PD
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On an I/V graph, a shallow gradient means what?
Greater resistance
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Does the resistance change on a filament lamp?
Yes, looks like an S
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Why does temperature cause resistance to increase?
Increase in temperature means atoms vibrate more, collide with electrons and they lose their energy.
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What are the three main semi-conductor components?
Thermistor, LDR and diode.
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What happens to the resistance in a thermistor as the temperature increases?
The resistance decreases
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What happens to the resistance as the light intensity increases in an LDR?
Resistance decreases
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Why does the light intensity and increase in temperature make the resistance decrease in these components?
The light intensity and increase in temperature provide energy that releases more electrons so more charge carriers are available.
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Describe the main feature of a IV graph on a diode
It has a threshold voltage, so it doesn't start at 0,0
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What is power?
The rate of transfer of energy
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What unit do electrical power companies use?
KiloWatt hours
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Give the equation they use to work of energy
Energy = power x time
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How many joules is one kilowatt hour equivalent too and why
3.6million joules, power = 1000joules(1KW) and Time = 3600 seconds (1hour)
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What equation do the companies use to work out cost?
Cost = number of units x unit price
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What is a fuse?
A wire connected between the live terminal and an appliance, which melts when the current gets too large.
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How do the Earth wire and fuse work together?
If the live wire touches the case, the current flows down the earth wire, the fuse then melts and cuts off the live wire.
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What is internal resistance?
The resistance that comes from a battery because of the electrons colliding into atoms during the chemical energy inside the battery
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What is The EMF?
Electromotive force, the amount of electrical energy the battery produces for each coulomb.
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Give 4 equations for EMf
EMF = V+Ir, EMF = V+v, EMF = I(R+r), V = EMF - v
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What does the Big and little R stand for in these equations?
R is resistance, r internal resistance
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What does the little v stand for in these equations?
Lost volts
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What is Kirchoff's First Law?
Total current enetering a junction = the total current leaving it.
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What is Kirchoff's Second Law?
Total EMF around a series circuit = the sum of the PD's across each component.
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What is the equation to work out total resistance in a series circuit?
R1+R2+R3=Rtotal
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What is the equaion to work out total resistance in a parallel circuit?
1/R1+1/R2+1/R3=1/Rtotal
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What is the equation of a potential divider?
Vout+ (R1/R1+R2) x Vin
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Card 2

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What is the equation for Current involving charge and time?

Back

Q=IT

Card 3

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What is a coulomb?

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Card 4

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What is drift velocity?

Back

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Card 5

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What is the equation for Drift velocity?

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