Paper 2 content Flashcards
Why is temperature constant when changing state
energy is used to overcome potential energy
Define thermal eqm
heat flow stops when it reaches the same temp.
what does ΔU +ve mean
the system gains internal energy
what does +ΔQ mean
system gains heat energy
what does ΔWD mean
work done by the system
define specific heat capacity
energy to raise 1kg of mass by 1 deg. without change of state
define specific latent heat
energy needed to change 1 kg of mass from one state to another without raising its temperature
what state to what state is fusion
solid to liquid
what state to what state is vapourisation
liquid to gas
similarity of gravitational and electric field [2]
- follow inverse sq. law
- use field lines to represents
- have equalpotential lines
differences between gravatational and electric fields [2]
- g-fields always attract
- electric field repels/attract depends on charge
- acts on different body (masses/charges)
define fields
a region at which a body experiences a non-contact force
What is the gravatational potential at infinity
0
main idea of Kepler’s 3rd law
T^2 = r^3
how to calculate potential difference
ΔV = Vf -Vi
gradient of potential and seperation
field strength
area under field strength and seperation graph
change in potential
define geosynchronous orbit
orbits in the same period as the planet’s
define geostationary
special e.g. of geosynchronous
stay above the same spot of the planet
name one use of low orbit
weather
direction of electric field lines
+ve to -ve
define absolute electric potential
WD per unit charge to bring it from infinity to point
What happens potential when moving closer to +ve charge
increases - as WD needed for +ve test charge to get closer
what happens to potential when moving away from +ve Q
decreases - no WD by test charge as there’s repulsion
what happens to potential when moving towards -ve Q
decreases - WD by field - as attracted
what is the effect of opposing electric field on capacitance
- greater electric field strength
- increases permitivity
- greater capacitance
RC and half life conversion
t1/2 = 0.69RC
define magnetic flux density
Force per metre of wire carrying 1A perpendicular to the field
Define Faraday’s law
emf is proportional to rate of change of magnetic flux
Define Lenz’s law
Direction of induced emf opposes the motion causing it (change of magnetic flux that causes it0
Unit for magnetic flux
Wb
Define magnetic flux
Amount of magnetic field passing through an area
What is magnetic flux linkage
the amount of magnetic field passing through a coil of wire
what is eddy current ?
heat loss caused by the opposing current produced
solution to eddy current
laminated core
- eddy current can’t pass through between layers
-amplitude of overall current is lower
3 sources of energy loss by transformers
- eddy current
- magnetizing and demagnetizing core
- resistance in coil
solution to energy loss to mag and demag core
use softer core - easier to mag and demag
solution to resistance in coil
use thicker wires
Why is ionising radiation dangerous?
- DNA alteration
- cell damage, mutation => cancer
- change func. of enzymes
Define radiation dose
energy absorbed per body mass
Define dose equivilent
the measure of damage done by radiation
Dose eq. = rad. weighing factor * dose
Application of alpha radiation
Smoke alarm
- allow current to flow
- won’t travel far
- when smoke present, alpha particles are intercepted
- triggering alarm
application of beta radiation
thickness detector
(thicker = less beta passes)
app. of gamma radiation
Radiotracers
- diagnose without need of surgery
- short half life + less ionising
Cancer treatments
- radiation damages cells
-high dosage targeted at centre of tumour
- shielding needed to protect staff
App. of Carbon-14
radioactive dating
- plants take in CO2 as part of photosynthesis
- plants stores the C-14 when they die
- could be used to date the plant
define binding energy
energy needed to split nucleus to its constituents nucleons
what is binding energy equivilent to ?
total mass defect
E(individual nucleon) > E( in nucleus)
Observation from binding energy - mass no. graph [2]
- three peaks - O, N, He most stable - multiple of alpha
- highest point - Fe (most stable nucleus)
- avg. binding energy increases rapidly initially
- decreases gradually as n. increases
E.g. material for fuel rod
Uranium -235
E.g. for moderator
- heavy water
- graphite
material for control rod
- boron
- cadmium
material for coolant
- water under pressure
- carbon dioxide
function of moderator
slows down fast neutrons - further fission
what is produced in a fission reaction
2 daughter nuclei + 2 or more neutrons
func. of control rods
slows down reaction by absorbing neutrons
2 main observation of rutherford scattering
- most alpha particles passes straight through
- some deflected at large angle
conclusion from rutherford scattering
- atoms have a very small centre
- nucleus contains almost all the mass
3 sources of background radiation
- radon gas
- cosmic ray
- naturally occuring iostopes
what processes occurs when too many protons
beta-plus decay
electron capture
what process occers when too many neutrons
beta-minus decay
Why is technetium-99m used for medical diagnose
- metastable - half life greater than 10^-9
- emits gamma
2 methods to determine the radius
- estimation by closest approach
- determination by electron diffraction
When does fission occurs
E(starting nucleus)> E(daughter)
When does fusion occurs
E(starting nuclei)<E(fused)
fission
what happens when mass < critical mass
fission eventually slows down
nuclear reactor
How to handle waste
- encased in cement
- store underground
- vitrification
- cooling in storage
- further encased with lead containers
nuclear reactors
3 precaution
- shielding
- reduce exposure
- remotely handle with tongs
- emergency shut-down protocol
3 pros of nuclear reactor
- no production of greenhouse gas
- highly reliable
- not weather dependent
nuclear reactors
3 cons
- dangerous
- expensive to handle waste
- have potential to cause catastophic consequence on envrionment and surrounding communities
Define mass defect
mass lost that is converted into energy
What is needed to be acc. when using GM-counter
- background
- corrected distance
Assumptions for kinetic theory model
- Volume of molecules are negligible
- Collision are elastic
- Collision time is negligible compared to time between collision
- No intermolecular forces between molecules
Why does a molecule exert a force on the wall of cylinder
- Direction changes for molecule
- Therefore change in momentum
- Resultant force acting on molecule
- Equal and opposite force acting on cylinder wall
