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Energy and types of resources, total energy (50J), useful energy (30J),…
Energy and types of resources
types of energy stores and energy transfers
energy stores
knetic
moving objects have energy in their knetic store
gravitational
objects gain energy in their gravitational potential store when they are lifted above ground
elastic
objects have energy in their elastic potential store if they are streched
electrostatic
objects with charge intercatin with one another have energy in their electrostatic store
magnetic
magnets interacting with each other have energy in their magnetic store
chemical
objects with energy in their chemical store can release energy in chemical reactions
nuclear
Atomic nuclei release energy from their nuclear store during nuclear reactions
thermal
all objects have energy in their thermal state, the hotter the object, the more energy it has in this store
energy transfers
radiation
Energy is transferred by electromagnetic waves, exp: light or sound
mechanical
when a force acts on an object exp: pushing
heating
heating can be transfered by
convection
To reduce energy transfers by convection, convection currents must be prevented from forming
Therefore, the fluid (liquid or gas) that forms the currents must be prevented from moving
who it works
When a fluid (a liquid or a gas) is heated:The molecules push each other apart, making the fluid expand
This makes the hot fluid less dense than the surroundings
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Convection is the main way that thermal energy is transferred through liquids and gases
radiation
The colour of an object affects how well it emits and absorbs thermal radiation
Shiny/white objects are the worst at emitting and absorbing thermal radiation
Black objects are the best at emitting and absorbing thermal radiation
The hotter object, the more infrared radiation it radiates in a given time
All bodies (objects), no matter what temperature, emit infrared radiation
conduction
insulation
a way of insulatig a house is by putting a cavity (hole) between 2 walls and adding a good insulator in the middle. This reduces conduction and convection
the effectivenes of an insulator depends on
conductivity
The lower the conductivity, the less energy is transferred
thickness
The thicker the material, the better it will insulate
density
The more dense the insulator, the more conduction can occur
In a denser material, the particles are closer together so they can transfer energy to one another more easily
Insulation reduces energy transfers from both conduction and convection
To reduce energy transfers by conduction, materials with a low thermal conductivity should be used, these are called insulators
metals are very good conductors, other materials as wood are bad conductors
transfered through the vibrations of atoms
the particles with more thermal energy pass on their energy to the particles surrounding them, causing the heat to spread from the hotter regions to the colder regions of the material
main method of energy transfer for solids
energy is transfered from a hotter object to a colder one
electrcal
a charge moving through 2 points of a circuit
energy
Energy is the capacity of something to do work
when there is change to a system energy is transfered
a system is an object or a group of objects
energy can't be destroyed or created
energy can be dissipated (spread out) by heating or radiation, this energy is not useful and is called wasted energy
exp of transfers of energy : bat hiting ball
moving bat has energy in its knetic store
energy is transfered mechaniclly to the ball, now the ball has a knetic store ( useful )
energy is dissipated by heating to the thermal store of the ball (wasted energy)
energy efficienty
the proportions of the energy supplied that is transferred in useful ways
The efficiency of a system is a measure of the amount of wasted energy in an energy transfer
formula
useful energy output/ total energy output x 100
Sankey diagrams
can be used to represent energy transfers
Sankey diagrams can be used to represent energy transfers
Sankey diagrams are characterised by the splitting arrows that show the proportions of the energy transfers taking place
the drawing needs to be proportional to the amount of energy
work done
Work is done when an object is moved over a distance by a force applied in the direction of its displacement
When work is done on an object, energy is transferred, this energy is measured in joules (J)
tenis ball bouncing
Work is done on a ball when it is lifted to a height
The energy is transferred mechanically from the ball's kinetic energy store to its gravitational potential energy store
The weight on the ball produced by the gravitational field does work on the ball over a distance
equation
work done (w) = force(f) x distance (d)
work done = energy transfer
Work done is equal to the change in kinetic energy or gravitational potential energy
gravitational potential energy
The energy an object has due to its height in a gravitational field
equation
gravitational potential energy (J) = mass( kg) x gravitational field (N/kg) x height (meters)
GPE = m x g x h
gravity on earth is 10
kinetic energy
The amount of energy an object has as a result of its mass and speed
equation
KE = 1/2 x m x v²
knetic energy (J) = 1/2 x mass (kg) x velocity² (m/s)
power
power is the amount of energy transfered in a certain amount of time
Power ratings are given to appliances to show the amount of energy transferred per unit time
equation
power(W) = work done (J)/ time(s)
p=w/t
measured in watts
p1/v1=p2/v2
pressure
pressure with gasses
volume
if there is less volume there will be more concentration and in order more collisions increasing the pressure
if volume is expanded pressure will decrease
concentration
If there are more particles there will be more collision meaning higher pressure
temperature
When heated up the energy gets passed into a kinetic energy store, this means that the particles are faster and have more force, meaning they have a higher pressure
gasses
total pressure will be affected by
how much energy per coalition
how many collisions
gases move in random directions and bounce, they exert a force (pressure) when bouncing
Pressure in a liquid
The deeper you go, the more pressure and the denser the liquid the more pressure
pressure difference (pa)=depth (m) x density (kg/m3) x gravity (m/s2)
When an object is submerged in a fluid, pressure will act on the object eventually and in all directions. This creates forces which act on the object act at 90 degrees to the surface of the object
Pressure(pa)= force(N)/area(m2)
the larger the surface are the less pressure
force per unit are, it can be measured in pascals o N/m
p1 times t1=p2 times t2
density
the mass per unit volume of a material
Density(kg/m) =mass (kg) x volume (m3)
density of water is 1
Absolute zero
IN kelvin -273 degrees is the absolute zero temperature
When a particle is in -273 kelvin the particle doesn't move
total energy (50J)
useful energy (30J)
wasted energy (20J)
in joules
in newtons
in meters
