Module 4-Electricity

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Define Current
The rate of flow of charge
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What is the equation for current?
I=Q/t
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What is the elementry charge?
The charge of an electron (1.6x10^-19)
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What is a charge carrier?
Electrically charged particles that are free to move in an object
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What is a substance that contains ions that conduct electricity called?
Electrolyte
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How many charge carriers do semiconductors and insulators have compared to metals?
Semiconductors have less and perfect insulators have none so they dont allow current to flow
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Define mean drift velocity
I=Anev
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How can you increase the current in a wire?
Increasing number of electrons, Increasing mean drift velocity of electrons
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Define potential difference
The work done to move a unit charge between those points
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What equation links Work done, Voltage and Charge?
W=VQ
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What equation gives the kinetic energy of an electron after it is accelerated from rest through a potential difference?
eV=1/2mv^2
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Define resistance
A componant has a resistance of 1ohm if a P.d of 1v makes a current of 1A flow through it
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What is the equation for resistance?
R=v/I
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What three factors effect resistance?
Length, Area, Resistivity
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How does length affect resisitance?
The longer the wire thqat more difficult it is to make current flow through it
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How does area affect resistance?
The thicker the wire, the easier it is for current to flow through it
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What is resistivity?
This is a measure of how much a material resists cureent flow
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What enviromental factors is resistivity dependant on?
Temperature and light intensity
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What is the equation for resistance including resisitvity?
R=pL/A
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What is an ohmic conductor?
Conductors that obey ohms law which states that current through an ohmic conductor is directly proportional to the potential difference providing the physical conditions remain constant
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What does the resistanxce of a theromosistor depend pn?
Temperature
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Describe the I-V characteristics of an ohmic conductor?
A straight line as their resistance does not change
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Describe the I-V characteristics of a filament lamp
a curve that is steep for small voltages but gets shallower as the voltage rises.
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Explain the I-V characteristics of a thermosistor
gets steeper as p.d increases, as current flows through the thermosistor heats up causing more charge carriers to be released so the resistance of the thermosistor decreases and the I-V characteristics become steeper
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What is a diode?
They are designed to only allow current in one direction, most diodes have a threshoild voltage of about 0.6volts in the foward direction before they will conduct
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Define Power
The rate of doing work
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What is the equation for power?
P=W/t
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What is the equation for power involving Voltage and Current?
P=VI
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What equations for power can be derived by substituting re-arranged ohms law into P=IV
P=I^2R, P=V^2/R
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What equation for energy links Voltage, current and timre?
W=VIt
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What unit is used for domestic energy?
Kilowatt hours
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How is the cost of domestic energy deduced?
Cost=no.of units x Price per unit
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What are some enviromental impacts of generating electricity?
Burning of fossil fuels releasing carbon dioxide into the atmosphere. Burning coal anf fuel also releases sulphur dioxide causing acid rain. Nuclear power staions produce radioactive waste which is dangerous to enviroment and human health
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List some energy saving devices
Energy saving light bulbs, LED light bulbs
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What is E.M.F?
Electromotive force is the total amount of work the battery does on each coloumb of charge
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What does the gradient and y-intercept on a V-I graph for a power supply show?
Gradient, -r. Y-intercept, E.M.F
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What is Kirchoff's first law?
The total current entering a junction is equal to that leaving it
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What is kirchoff's second law?
The total e.m.f arounf a series circuit is equal to the sum of the p.ds across each componant
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How can the resistance of a circuit in series be calculated?
R=R1+R2+R3
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How can the resistance of a circuit in parallel be calculated?
1/R=1/R1+1/R2+1/R3
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What is a potential divider?
A cicruit with a voltage source and a couple of resistors in series
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Other cards in this set

Card 2

Front

What is the equation for current?

Back

I=Q/t

Card 3

Front

What is the elementry charge?

Back

Preview of the front of card 3

Card 4

Front

What is a charge carrier?

Back

Preview of the front of card 4

Card 5

Front

What is a substance that contains ions that conduct electricity called?

Back

Preview of the front of card 5
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