TOPIC 1 ENERGY Flashcards
what are the nine types of energy?
Electrical energy Light energy Sound energy Kinetic energy Nuclear energy Thermal energy Gravitational potential energy Elastic potential energy Chemical energy j
what is electrical energy (example)
it’s energy from when a current flows
what is light energy (example)
light bulbs, sun energy
what is sound energy (example)
energy from loudspeakers
give an example of kinetic energy
anything that moves
give an example of nuclear energy
energy released from nuclear reactions
give an example of thermal energy
energy that flows from hot objects to colder ones
give an example of GPE
possessed by anything which can fall
give an example of elastic potential energy
possessed by springs , elastic, rubber bands…
give an example of chemical energy
foods, fuels, batteries…
what is energy measure in ?
joules (j)
what are the forms of stored energy
potential and chemical energy - this type of energy is waiting to be turned into other forms
what is the principle of the conservation of energy?
Energy cannot be created or destroyed, only transferred.
+ energy is only useful when it can be transferred from one form to another e.g stored energy
how do you calculate efficiency?
(output energy/ input energy) x100
what makes a device insufficient
all mechanical devices experience friction - energy is lost as heat
what is work done measure in ?
joules (j)
what is the unit of measure for power?
Watts (W)
what is energy measured in?
joules
what is mass measure in ?
kilograms (kg)
what is distance measured in ?
metres (m)
what is force measure in ?
newtons (N)
what is one measure in?
seconds (s)
what is speed measure in ?
metres / second
what are the units for acceleration
metres / seconds squared
Define energy
Energy is the capacity to do work- measured in joules.
Define work done
work is when you are moving a subject over a certain distance, with a certain force. This movement is called work.
How do you work out work?
work done (j) = force (N) x distance (m)
what is work done equal to?
energy transferred
what is gravitational field strength on earth
10N
how do you work out GPE
GPE(N) = mass (kg) x gravitational field strength (10N) x height (m)
how do you work out kinetic energy?
KE = 1/2 mass x velocity squared
what is the relationship between gravitational potential energy and kinetic energy
when something falls it’s GPE is converted to KE as the further it falls, the faster it goes - kinetic energy gained = GPE lost.
what is power
power is the rate of doing work
how do you work out power
power = work done / time taken
what is power measured in ?
watts (or joules)
power = how much energy per second, so, watts = joules per second
what are the main features of a power stations (fossil fuels)
generators of electricity, boilers, turbines and condensers
what are the problems with fossil fuel power stations
global warming and air pollution
calculation of average power
P=Fv
power = force x velocity
How do you calculate breaking distance (m)
Breaking distance (m) = Kinetic energy (j) / force (N)
How do you calculate height ?
height = KE / (mass x gravity)
how do you work out time?
time = energy / power
how do you work out energy transferred ?
energy = power x time
what is conduction ?
conduction of heat is the process where vibrating particles pass on their extra kinetic energy to neighbouring particles - conduction of heat mainly happens in solids
why is conduction best in metals
it’s best in metals as they have free electrons
what is convection
convection occurs when the more energetic particles move from the hotter region to the cooler region and take their heat energy with them - the circulation of a fluid by heating.
what is radiation
thermal or infrared radiation involves the emission of electromagnetic waves of a certain range of frequencies. It’s next to the visible light of the electromagnetic spectrum. All objects constantly emit and absorb heat energy.
how does conduction work?
Atoms vibrate and pass on the vibrations to the nearest atom by colliding and ‘shaking’ them- because of this conduction take place best in solids where particles are closer together.
How does convection occur ?
Heating a fluid makes it less dense and therefore the hot fluid rises. When it rises, it starts to cool and falls back down to the heat source causing a convection current. This circulation continues until the fluid is an equilibrium.
what objects emit infrared radiation?
all objects that are above absolute zero (-273C or 0K) emit infrared radiation.
hotter objects emit more
how does infrared energy travel
travels in electromagnetic waves and which is why it can travel in a vacuum as it does not need particles to be transferred
what objects reflect infrared radiation
light coloured, shiny, smooth objects
what objects absorb infrared radiation the best
dark coloured, rough/ matt surfaces
what role does convection take place in everyday phenomena
costal wind is caused by convection currents. Air above land warms up quicker than the air above the sea. The air above the land rises and moves towards the sea, cools and moves back towards the land causing an inward wind. This cycle is reversed at night.
how is insulation used in buildings
insulation is used to stop heat transfers
examples:
double glazed windows- the two layers of glass with a narrow air gap in between which reduces conduction and convection
cavity wall insulation- the foam in between the bricks stop convection currents being set up in the gap and radiation across the gap. the insulating foam contain small air pockets which reduce heat loss by conduction and convection
how is insulation used to reduce heat transfer in the human body
1) when your body is cold your hairs on your skin stand up and trap a thicker layer of insulating air around the body. this limits heat loss by convection
2) humans have layers of fat under their skin to insulate their body
3) layers of clothes reduce heat transfer- the pockets of air trapped in the clothes and between layers mainly reduce heat transfer by conduction and convection- they also reduce heat loss from your body by radiation as some materials absorb heat radiated out by our bodies.
