Physics (Jones) Flashcards
What are the different base unit quantities and what they are measured in
Mass (Kg)
Length (M)
Time (S)
Electrical current (A)
Tempureture (K)
Amount of substance (mol)
METAL
What are the prefixes and there ^ to 10 and there symbols
Peta (P) 10^15
Tera (T)10^12
Giga (G) 10^9
Mega (M) 10^6
Kilo (K) 10^3
Deci (d) 10^-1
Centi (c) 10^-2
Milli (m)10^-3
Micro (u) 10^-6
Nano (n) 10^-9
Pico (p) 10^-12
Feunto (f) 10^-15
What are the base measurements and there units
Kilograms (Kg)
Kelvin( K)
Amperes (A)
Metre (M)
Moles (mol)
Candela (cd)
Seconds (s)
MACKS
Homogeneity definition
Where an equation has the same base units on both sides of the equals
Definition of error
The difference between the result and real value
What are the 2 types of error and what are there properties
Radom - always humans fault (parellex error)
Systematic - differs the same amount each time for an incorrect results
Definition of random error and type of error
It’s a humans fault
Type:
Parallax error
Definition of a systematic error and type
The result differs by the same amount each time for am incorrect result
(Zero) error
Definition of Resolution
The lowest increment of measurement
What is absolute uncertainty
If we only have one measurement the absolute uncertainty = resolution
If we have multiple measurements the absolute uncertainty = range\2
Percentage uncertainty equation
Uncertainty/mean * 100
The value we give and the absolute uncertainty must have the same number of decimal places
What is combined uncertainty
Absolute uncertainty 1 + absolute uncertainty 2
Rules of combined uncertainties
If quantities are added or subtracted we always add the uncertainties together
What do we do if we are multiply or dividing uncertainties
We add the percentage uncertainty of the quantities to calculate the uncertainties we want
What is current
Rate of flow of charged particles
If its metals it will be electrons
What is the equation that links current to change and the units
Q=It
Current (a)=
Charge(c)/time(s)
Quantisation of charge equation and what each letter stands for
Q=ne
N is number of electrons/ protons
E is elemental charge
Q is charge
What is elemental charge
1.6x10^-19
What direction does conventional current go
Positive to negative
What direction do electrons flow
Negative to positive
When we have a circuit going into the solution what moves
The ions move
What is Kirchhoffs first law
{current(I) in = {current(I) out
Sum of currents in junction are equal to sum of the current out the junction
This is true because of conservation of charge
What happens to the particles in a wire with no charge going through them
They vibrate around a fix point
Free electrons can’t move in the wire so no overall movement
What happens to the particles in a wire if a charge is flowing through them
If we plug a wire into a circuit - apply a potential difference across the wire then the free electrons move along the wire
And there is net movement overall
There is displacement along the wire
What is another equation for current that isn’t Q=IT
I = nAVe
I= current(A)
n= number density (m^3) [cm^-3]
e=elemental charge (C)
V = mean drift velocity
What is the number density for a conductor and what are two conductors
X10^28 m^-3
Copper
Zinc
What is the number density of a semiconductor
X10^15 - x10^q8
Silicon
Germanium
What is the number density for an insulator
Polyethylene
Wood
0m^-3 - 100m^-3
What is potential difference
The energy gained or transferred by charge carrier
What is the equation for potential difference
Potential difference(volt) = energy gained(joules) / charge(coulombs)
V(V) = E(J) / Q(C)
Potential difference = work done / charge
V = W/Q
What is 1 amp equivalente to and 1 volt equivalent to
1 amp = 1 coulomb per second
1 volt = 1 joule per coulomb
1V = 1JC^-1
What happens in a battery
Work is done at the charges
Charge gaining energy as it transfers from chemical energy to electrical energy
Potential difference of a cell battery is called emf (electromotive force)
When work is done by the charges
What happens in an electron gun
Electrons gain energy
They accelerate
Therefore velocity increases
What is ohms law
V = IK
At a fixed temperature
V = I
Resistance = R
How would you write an I-V characteristic 6 marker
Measures the current(I) with the ammeter
Measure the potential difference P.D (V) with the Volt meter
Calculate resistance with
R=V/I
Increase p.d on the variable power supply
Repeat steps 1-4
Switch wires on power supply two get negative values
Repeat steps 1-5
What are properties in a circuit with a filament lamp in it
V increases + I increases but by less per volt at higher currents because resistance increase
Temperature increases
Ions vibrate with greater amplitude and greater frequency causing more collisions with free electrons
What are properties of a circuit with a diode in it
PD is negative the current is 0 amps as resistance is infinite
PD is positive the current remains at 0-1A until threshold voltage
The resistance decreases so the current increases the
n(number density per m^3) Value increases
What are characteristics of a thermistor
There is a negative temperature coefficient
As temperature increases
Resistance decreases
What are characteristics of a LDR
Negative coefficient of light intensity
Light intensity increases
Resistance decreases
Why does light intensity and temperature have a negative coefficient
Thermistors and LDRs work by as temp or light increase they release more free electrons
So a greater current can flow at resistance decrease
Increase the ‘n’ value
N = number of charge carriers
What does resistance depend on
Length and area
What is equation for the proportions of area and length
R= L/A
Equation that links resistivity and resistance
R = xL/A
What happens to potential difference in a series circuit
P.d splits
What happens to potential difference in a parallel circuit
Potential difference is the same in every branch of a parellel circuit
What is the equation that links potential difference energy and charge
V = E/Q
What happens to current in series
Current stays the same
What happens to current in parallel
It is split along the branches
What is the equation for resistance in a series circuit
V=IR
What is the equation for resistance in parellel
1/R + 1/r2 + 1/r3 = 1/Rt
What is emf
The work done on charges
Energy gained per unit charge
What is voltage equal in a system with internal resistance
V = terminal p.d
The potential difference measured across terminal of a cell when a circuit has a current through T it
What is Ir equal to
It is the work done by charges travelling through out the cell
P.d the internal resistance
What is the p.d across the internal resistance also called
Lost volts - potential difference across the internal resistance of the cell
What is emf equal to
Terminal p.d + lost volts
What is the definition of voltage
Work done by the charges
What is the internal resistance
Resistance of Source of emf
What does the internal resistance cause
Some energy to be transferred as thermal energy
What do volt meters read when there is internal resistance
Terminal pd - the amount of energy used to leave the battery
What happens to p.d when no current is flowing through a circuit
No volts are lost so emf=V
What happens to p.d as current increases
P.d decreases because more volts are lost
What is Kirchhoff second law
In any closed loop of a circuit
Sum of emf = sum of p.d
How is p.d distributed in a circuit
In the same ratio as resistance
What is the equation for potential dividers
V1/V2 = R1/R2
What is v out equal to
V out = R2/R1 +R2 x V in
What is total resistance equal to
R1 + R2 = R total
What is total p.d equal to
V total = V1 + V2
What does potentiometer do
Controls voltage in a circuit
