TOPIC 1 ENERGY

Question 1

what happens when energy is transferred to an object

Answer 1

the energy is stored in one of the objects energy stores

Question 2

name different type of energy stores

Answer 2

thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic , electrostatic, nuclear

Question 3

how is energy transferred
1- mechanically
2-electrically
3- heating or radiation

Answer 3

1- force doing work
2-work done by moving charges
3-light or sound

Question 4

what is a system

how does it transfer energy

Answer 4

a system is a single object(the air in a piston) or a group of objects (two colliding vehicles),

when a system changes - energy is transferred into or away from the system between different objets in the system or different energy stores

Question 5

what is a closed system

Answer 5

systems where neither matter nor energy can enter or leave, the net change in the total energy of a closed system is always 0

Question 6

how is energy transferred by heating (kettle example)

Answer 6

boiling water in a kettle-
water is the system
energy is transferred electrically to thermal energy store of kettles heating element
energy is transferred to water by heating to water’s thermal energy store (causing temperature to rise)

Question 7

how is work done

Answer 7

another way of saying energy transferred, work is done when current flows
(work is done against resistance in a circuit )
or by a force moving an object

Question 8

what happens when a person throws a ball upwards

Answer 8

energy transfer from chemical energy store of person’s arm to the kinetic energy store of the ball and arm.

Question 9

what happens when a ball is dropped from a height

Answer 9

a ball dropped from a height is accelerated by gravity.the gravitational force does work, energy is transferred balls gravitational energy store to its kinetic energy store

Question 10

what happens when a car slows down

Answer 10

friction between car brakes and wheels does work as it slows down.
energy transfer happens from wheels kinetic energy store to thermal energy store of surroundings

Question 11

what happens between car and stationary object

Answer 11

normal contact force between car and object does work - energy is transferred from car’s kinetic energy store to other stores e.g. elastic potential , thermal energy store of object and car body. - some energy might be transferred away by sound waves

Question 12

when is energy transferred to kinetic energy store?
when is energy transferred away from this store?
what does the amount of energy in a kinetic energy store depend on ?

Answer 12

when an object speeds up (anything moving has energy in its kinetic energy store, )-
energy is transferred away from this store when an object slows down
the energy in the ke store- greater the mass: faster is goes, more energy in store

Question 13

how to calculate kinetic energy store

Answer 13

1/2 x mass x speed^2

Question 14

how is energy transferred to gravitational potential energy store?
what does the amount of energy is gpe store depend on ?

Answer 14

lifting objects store energy in gpe store - lifting requires work.
the higher the object is lifted, more energy is transferred
amount of energy depends on objects mass height and strength of gravitational field the object is in

Question 15

how to calculate gpe

Answer 15

mass x gravitational field strength x height

Question 16

what happens when an object falls

Answer 16

energy transfers from gpe store to kinetic energy store

energy lost from gpe store = energy gained in kinetic energy store when there is no air resistance

in real life =air resistance acts on all falling objects, so some energy goes to other stores like thermal store of object and surroundings

Question 17

what happens when something is stretched

how can you find the elastic potential energy of a stretched spring

Answer 17

stretching ot squashing an object causes energy to transfer to elastic potential energy store

as long as the limit of proprtionality has not been exceeded, you can find the elastic potential energy store of a stretched spring - 0.5 x spring constant x extension^2

Question 18

what is specific heat capacity

how do you calculate it

Answer 18

the amount of energy needed to raise the temerature of 1kg of a substance by 1 degree celsius

materials that need to gain lots of energy in their thermal energy stores to heat up also transfer lots of energy when they cool down

change in thermal energy = mass x shc x temp change

Question 19

SPECIFIC HEAT CAPACITY PRACTICAL

Answer 19

1- solid material (e.g. copper) block of material w 2 holes in it for heater and thermometer- put heater in one hole, thermometer in a hole

2- measure mass of block, wrap it in insulating material (newspaper) to reduce energy transferred t surroundings

3- measure initial temp of block, set p.d. of power supply to 10 V- turn on supply start stopwatch

4-when power is on, current does work , transfers energy electrically from power supply to heaters thermal energy store. then goes to materials thermal store by heating. materials temp rises

as block heats- note temp and current every min for 10 mins (current should not change )

with readings calculate power with p.d x current

calculate energy at each temp with power x time

plot graph of energ transferred (x axis) to block , temp (y axis)

gradient is temp change/ thermal energy change

shc= 1/ gradient x mass of block

Question 20

what is wasted energy?

Answer 20

when energy transfers between stores, not all is transferred usefully, some energy is dissipated. (usually thermal energy stores)

e.g. for phone. energy is usefully transferred from chemical energy store but some is dissipated to thermal energy store of phone

Question 21

energy transfers for closed systems?

Answer 21

e.g. cold spoon in soup in sealed flask. spoon and soup make closed system. energy transfers from thermal store of soup to useless thermal store of spoon- soup cools down a bit - energy transfers in system but no energy lost. net change is 0.

Question 22

what is power how is it calculated

Answer 22

power is the rate of energy transfer/ doing work

measured in watts - 1 watt = 1J of energy transferred

power = energy transferred or work done / time

a powerful machine transfers a lot of energy in a short amount of time

Question 23

whats conduction

Answer 23

when vibrating particles transfer energy to neighbouring particles

occurs mainly in solids

energy transferred to object by heating goes to thermal store of object. energy is shared inbetween kinetic energy store on particles in object- - particles in heated part of object vibrate and collide more

continues until energy is transferred to other side of object - then goes to thermal store of surroundings

Question 24

what is thermal conductivity

Answer 24

a measure of how quick energy transfers through a material by conduction.
high thermal conductivity means energy is transferred between particles quicker

Question 25

whats convection

Answer 25

when energetic particles move away from hotter to cooler regions
-happens in liquids and gases- when u heat gas or liquid, particles move faster. space between particles increase. causes density of region to decrease.

bc liquids and gases flow , yhe warmer less dense region will rise above dense, cool region.

if theres a constant heat source. convection current will be created.

Question 26

how do radiations make convection currents

Answer 26

1- energy is transferred from radiator to near air particles(that collide w radiation surface) by conduction.

2- air by radiaor becomes becomes warm and less dense. particle move quicker- more space

3- warm air rises , replaced by cooler air - cool air is heated by radiator
4- previously heated air transfers energy to surroundings e.g walls - it cools , goes denser, sinks

this repeats making a convection current

Question 27

what causes unwanted energy transfers

Answer 27

when something moves theres at least one frictional force acting on it , - this causes energy to be dissipated, or air resistanct can transfer energy from object’s kinetic store to thermal store.

Question 28

how to reduce unwanted energy transfer

Answer 28

usually liquids like oil- flows easily between objects and coats them -

for objects that are rubbed together. they reduce friction between objects surfaces when moving,

Question 29

how to reduce energy transfer in homes

Answer 29

thick walls with material of low thermal conductivity. - slower rate on energy transfer, builing cools more slowly
cavity walls- made from inner & outer wall with gap- air gap reduces energy transferred by conduction through wall- gap made from foam- reduces energy transfer by convection in wall cavity

loft insulation can reduce convection currents being created in lofts

double glazed window - air gap betwee two sheets of glass to prevent energy transfer by conduction through window

draught excluders around doors and windows reduce energy transfers by convection

Question 30

practical - how to investigate effectiveness of materials of thermal insulators

Answer 30

1- boil water in kettle , pour water in sealed container, - measure mass of water in container

measure initial temp w thermometer

seal container leave for 5 mins (w stopwatch) remove lid, measure final temp.

pour away water, allow container to cool to room temp

repeat but wrap container in different material( e.g. foil, newspaper) once sealed - use same mass of water at same initial temp each time

(lowe the temp difference, better the material as thermal insulator )
e.g. bubble wrap, wool is good

or thickness- the thicker- better insulator , the smaller the temp change , less energy transferred -

Question 31

efficiency

how do you work out efficiency

Answer 31

the less energy that is wasted , the more efficient the device is said to be. - improve efficiency by insulating objects, lubricating them, making them more streamlined,

no device is 100 percent efficient, wasted energy usually goes to thermal

useful output energy transfer/ total input energy transfer

or
useful power output/ total power input

Question 32

give an example of something that is 100 percent efficient

Answer 32

electric heaters- all energy goes to electrostatic energy store is transferred to useful thermal energy store

Question 33

what is non renewable energy resources, give examples

Answer 33

resources that will run out one day, damage environment, provide most of our energy

. fossil fuels and nuclear fuel (uranium and plutonium)
fossil fuels are natural resources that form underground over millions of years- burnt to provide energy

main fossil fuels
coal
oil
natural gas

Question 34

what are renewable energy resources

give examples

Answer 34

will never run out, energy can be renewed as it is used - damage environment less that non renewable
dont provide much energy
some are weather dependent

(sun, wind, water waves, hydro electrcity, bio fuel, tides, geothermal )

Question 35

how are energy resources used for transport

Answer 35

non renewable- petrol and diesel powered vehicles use fuel from oil
or coal in steam trains to boil water for steam

renwable- vehicles run on pure bio fuels or mix of biofuel-renewable, petrol,diesel

Question 36

how is energy resources used for heating

Answer 36

non renweable
natural gas is used as fuel for heating homes, gas used to heat water - pumped into radiators
/coal burnt at fireplace
/electric heaters use electricity generated from nr energy source

renewable
geothermal heat pump
to heat buildings,/ solar water heaters- sunt to heat water thats pumped into radiators of building,/
burning biofuel or using electiricty generated from renewable source to use for heating

Question 37

what is wind power?

strengths and weakness of wind power

Answer 37

turbine has generator that rotates blades to produce electricity

strengths
no pollution (only a bit when manufactured)/ no fuel costs & minimal running costs/ no permanent damage to landscape- when removed noise is removed

weakness
spoil the view- big effect of scenery/ noisy/ weather dependent- imposible to increase supply if wind stops

Question 38

solar cells - strengths and weakness

Answer 38

generate electric currents directly from sunlight

strenghths-
no pollution/ reliable source of energy in sunny countries/ after initial costs it is free and running costs almost nil

weakness
requires a lot of energy to manufacture/ only useful in daytime/ cant increase power output when in extra demand / generates electricity on small scale/ initial costs r high

Question 39

hydro electric power strengths and weakness

Answer 39

requires flooding of a valley by building a big dam- water is allowed out through turbines

strengths- no pollution, it can provide an immediate response to icreased demand for electricity, no problem with reliability except in time of drought , no fuel costs and minimal running costs

weakness- flooding of valley can cause rotting of vegetation releasing methane and co2/ loss of habitat for some species/ reservoirs can look very unsightly when they dry up / initial costs are very high

Question 40

wave power strengths and weakness

Answer 40

located around the coast- wave powered turbines are connected to generator

strengths
no fuel costs, minimal running cost, no pollution, very useful on small islands

weakness- disturbs seabed and habitats of marine animals/ spoils view/ hazard to boats, unreliable as wave dies ou when wind drops/ initial costs are high / doesnt provide energy on a large scale

Question 41

tidal barrages

Answer 41

big dams built across river estuaries with turbines in them- tide comes in and fills estuary-water is allowed out through turbines at controlled speed

strength-
happens twice a day without fail so it is reliable always near predicted height/ no pollution/ no fuel costs and minimal running cost

weakness-
prevents free access to boats/ spoils view/ alters habitat/ height of tide is variable so low tides provide less energy that big ones/ dont work when water level is same either side of barrage(happens 4x due to tides)

Question 42

biofuels
and its strengths and weaknesses

Answer 42

renewable energy resources from plant products or animal dung - burnt to produce electricity or run cars
(debate on whether it is carbon neutral or not bc youre burning things at the rate u are growing things)

strengths- fairly reliable, crops take a relatively short time to grow, biofuels are continuosly produced and stored for when they are needed

weakness- cannot respond to immediate energy demands , cost to refie biofuels are very high, worry that growing crops for bio fuels means there wont be enough sace or water to meet demands for crops that are grown for food, large area of forests is cleared for bio fuels so lots of loss of natural habitat, decay of vegetation increases co2 and methane emissions

Question 43

non renewables e.g. fossil fuels and nuclear energy weakness and strengths

Answer 43

strengths- reliable- enough to meet current demand, extracted from earth at a afast enough rate , power plants repond quickly to changes in demand/ runnning costs are not expensibe

weakness- fuels are slowly running out if no new resources are found then stocks may run out in hundred of years , set up costs can be quite high
-coal oil gas releases co2 into environment adding to greenhouse affet adding to global warming
- burning coal and oil releases sulfur dioxide which makes acid rain - harmful to ecosystems
- coal mining causes mess to landscape
-nuclear waste is dangerous and difficult to expose of
- oil spillages affect environment and habitats
- overall cost of nuclear power is high c of cost of power plant and final decomissioning
- nuclear power can causes disasters

Question 44

explain use of fossilfuels in the uk

Answer 44

over 20th century- use of electricity increased as population grew, people used energy for more things,

begining of 21st century- electricity use drecreasing as appliances are most efficient and more careful with energy in our homes
most electricity from fossil fuels from nuclear power
fossil fuels- oil to fuel cars, gas to heat homes and cook foods

we are trying to increase use of reneweable sources

Question 45

why do people want to start using mor erenewable energy resources

Answer 45

fossil fuels are very damaging to the environment, non renewables will run out one day,

pressure from other countries and publi to intriduce targets for using renewable resources

pressure on energy providers to build new power plants to use renweable so they dont lose business or money

car companies affected- electric cars and hybrids on market and popularity is increasing

Question 46

how is the use of renwables limited

Answer 46

money- building non renewable power plants costs money- energy providers are reluctant bc fossil fuels are so cost effective, cost of switching will have to be paid

people dont want to live near wind farms etc

energy resources like wind power are not reliable as they cant increase
power output on demand

improviing reliability and cost of renwables takes time and money-

personal changes can be quite expensive, hybrid cars r expensve, solar panels r pricey,

Question 47

geothermal energy
strengths and weakness

Answer 47

occurs in volcanic areas where hot rocks lie near to the surface. it is the slow decay of radioactive elements e.g uranium deep inside earth

good- free energy that is reliable, little damage to environment, for generating electricity and heating buildings

bad- not many suitable locations for power plants , cost of building a power plant is high compared to amount of energy it produces