MODULE 4: ELECRICITY Flashcards
Ampere equation
I = Q/t
What is a conducting liquid called
Electrolyte
What is a coloumb
Electric charge
What is the charge of an electron, and it’s quantised version
1.6 x 10e-19 , +1e
What is conventional current
When current flows from positive negative, the holes left by the moving electrons
Kirchhoffs 1st law
Current going into a junction is the same as the current out
CONSERVATION OF CHARGE
What is mean drift velocity
Average velocity of electrons along the length of the wire, direction of force
What is number density
Number of charge carriers per unit volume of material
Number density equation
I=Anev
What are semiconductors
Metal conductors which have a less number density than normal metal conductors
Battery symbol
Two cells line and thicker one for negative
diode symbol
triangle and line on right
Thermistor symbol
Resistor with flat and diagonal line through
Variable resistor symbol
Resistor with arrow through
Resistor symbol
Rectangle
Fuse symbol
Rectangle with line through it
LDR symbol
Small resistor with two arrows points from top left
Filament lamp symbol
Circle with x
Led symbol
Diode with two arrows going out to top right
What is potential difference
Energy transferred from electrical components to other forms like heat etc, per unit charge
What is electromotive force
Energy transferred from the battery/cell to the electrical components
Voltage equation with energy
V = WORK DONE / COULOMB
What is an electron gun
Device to accelerate electrons to high speeds
What is inside a electron gun
A filament and anode which have a potential difference.
Electrons are fired through and get speed from the pd, then go through a VACUUM inside a glass tube
Electron energy formula in electron gun
Ve = 1/2 mv^2
Because v=energy/coulomb, Ve = energy
Resistance equation
R = V / I
What is ohmic conductor and what’s ohms law
Resistance is constant
For metallic conductor at CONSTANT temp, current in write is directly proportional to the potential difference across it
IV graph equation for resistor
Y=X
IV graph shape for filament lamp
Straight line with curves going to line parallel to x axis at each top and bottom y
‘_/‘ to midpoint then ‘/-‘ where dashes are curved, ie not straight appears only in middle of graph
Diode IV shape
Flat until a voltage threshold where is rapid increase.
What is diode bias
Which way the current goes through
What is resistivity and equation
Material property of how well it conducts, lower meaning better (let’s more current).
R= pL/A
How does temperature affect metals
Higher resistance hit each other more making less current
How does temperature effect semiconductors
lower resistance because more charge carriers
What is a thermistor
Resistor that depends on temperature
What other type of thermistor and what does it do
NTC thermistor
Negative temperature coefficient
what does NTC thermistor do
Resistance decrease as temperature increases
What is LDR and its properties
Light dependent resistor,
Resistance decrease with more incident light
What is electrical power and equation
P=IV
Rate of electrical energy transfer
What is the kilowatt hour
Energy transferred by device with a power of 1000watts in one hour
kWh = kW * hours
Resistance in series vs parallel
Series sum, parallel inverse sum
Work done equation in terms of potential difference
W=V * Q
Kirchhoff second law
In a closed loop
Sum of electromotive forces equals sum of potential differences
What is terminal pd
Pd across terminals of cell (ie whole circuit)
What are lost volts
Voltage around internal resistance
Electromotive force equation
E = IR + Ir = I(R + r)
What is a potential divider circuit
a simple circuit which takes advantage of the way voltages drop across resistors in series
output pd is taken across a component (which is some of resistor)
Potential divider circuit equation
Vout = (Vin * R2)/(R1+R2)
What is number density and unit
Number of electrons per volume
m^-3
