Paper1 Flashcards
Kinetic energy
0.5xmassxvelocity2
Gravitational potential energy
Mass x height x gravitational field strength
Power (2)
Energy transferred/time
Or
Work done/time
Insulation types
Cavity wall
Double glazing
Both use a layer of air to reduce heat loss from homes
Efficiency
Useful output/total input x 100
What is the current
A flow of electrons flowing through a circuit
What is potential difference?
Force propelling the electrons forward into the circuit
Bulb characteristic lines
Resistor - directly proportional
Bulb-flimsy line as temperature effects the resistance
Diode-line only positive as current can only go one way
Mains electricity
230v
50hz
Wires in plug
Earth wire (green-yellow) used for safety if plug casing ever went live
Live wire (brown) carries current
Neutral wire(blue)completes circuit
Power equation with PD
Potential difference x current
Power
Current
Current2x resistance
Energy
Electricity
Power x time
Or
Charge x potential difference
Energy transfer pendulum
GPE is transferred to KE as the pendulum swings down . KE transfers to GPE as it swings up .
Energy loss occurs due to thermal energy
When is work done?
When energy is transferred from one store to another
Fossil fuels
Non sustainable
Polluting
However
Fossil fuels are more reliable
Can meet energy demands
Relatively cheap
Nuclear power
Non renewable
Produce nuclear waste that must be stored for over a thousand years
Dismantling a power plant takes a long time
However
Extremely reliable
Does not contribute to climate change
Energy mix
Until 1950s coal was used
By 1980s 20 percent of power was nuclear
In 1970s scientists began to realise the effects of fossil fuels.
UK is lucky can can establish lots of wind farms and HEP plants
Reliability holds back renewable energy sources
PD in a series circuit
Total Pd Across all components are equal to that of the power supply
PD in parallel circuit
Each component including a power supply have the same PD
LDR
In dark conditions the resistor has a high resistance
In light conditions the resistor it has a low resistance
Thermistor
The resistance of a thermistor will decrease when temperature increases
what is the main benefit of AC
Can use a transformer to increase or decrease the PD
National grid
Electricity passes through a step up transformer maximizing voltage reducing energy loss
When reaching the house the PD goes through a step down transformer reverting the PD back to normal
Static electricty
If you rub 2 insulators together the friction caused will transfer electrons from one material to another . This positively charges one and negatively charges another
Electric fields
Each charged object generates an electric field.
If 2 objects of the same charge are placed next to each other a force of repulsion will occur
What way do electrons flow?
Negative to positive
What do resistors do
Reduce the flow of the current
Density equation
Mass/volume
Solids
Liquids
Gases
DENSITY
Solids-because particles are tightly packed together they have a lot of mass for their volume
Liquids-because their particles are still close together they have a lot of mass for their volume
Gases have a very low mass for their volume as the particles are not near each other
Internal energy
All 3 states have internal energy
It is made up of kinetic energy and potential energy (chemical bonds and intermolecular forces
What is specific latent heat
Amount of energy needed to the state of 1kg of a substance
Solid to liquid
Liquid to gas
Specific latent heat of fusion
Specific latent heat of vaporisation
How do you increase the pressure of a gas ?
Increase temperature will increase the number of particles colliding on the walls of the container
Work done on a gas
If we compress a gas then work has been done because we have applied a force onto a gas causing energy to be transferred to the particles increasing the internal energy store
Radius of atom
1x10-10m
How can electrons change energy lvl
If an electron absorbs EM radiation then it will have enough energy to move to the next energy level. It will emit that radiation losing energy and will move back down
What is radioactive decay ?
A total random process. When an isotope has an unstable nucleus radiation is emitted
What is activity ?
The rate at which a source of unstable nuclei will decay
Alpha particles
Highly ionising
Can only travel 5cm in the air
Stopped by a sheet of paper
Beta
Can travel 15 cm in air
Quite ionising
Stopped by a few mm of alluminuim
Gamma
Can travel several metres
Stopped by 2 m of led
Not very ionising
Half life
The time it takes for half of the radioactive material to decay
